Cover sheet, steel structure, and method for repairing steel structure

Abstract

To provide a UV-resistant cover sheet for covering steel materials and the like of steel structures located outdoors, a steel structure with the cover sheet, and a method for repairing the steel structure.SOLUTION: Provided is a cover sheet used for covering steel materials, the cover sheet including a barrier layer, a design layer, and a weather-resistant layer, and having a maximum spectral transmittance of 1.0% or less in the wavelength range of 300 nm or more to 350 nm or less.SELECTED DRAWING: Figure 2A

Description

[Technical field]

[0001] The present disclosure relates to a covering sheet, a steel structure, and a method for repairing a steel structure. [Background technology]

[0002] Steel structures such as bridges contain steel materials. Steel materials deteriorate over time due to corrosion. Deteriorated steel materials become defects that can significantly reduce the strength of steel structures. For this reason, steel materials are laminated with multiple coating films to suppress corrosion. Examples of coating films include multiple undercoat layers containing epoxy resin, a middle coat layer containing fluorine-based resin, and a top coat layer containing fluorine-based resin.

[0003] Steel structures are inspected periodically. If defects are found during the inspection, the steel materials are repaired. Recently, as in Patent Document 1, it has been proposed to repair steel structures by covering the steel materials with a covering sheet made of resin or the like. Patent Document 1 discloses a laminate including a fluororesin layer. Patent Document 1 proposes to facilitate the repair of steel structures by repairing the steel structures by covering the steel materials with a laminate. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2020-179569 A Summary of the Invention [Problem to be solved by the invention]

[0005] There are cases where outdoor steel materials, such as steel materials of outdoor steel structures such as bridges, are required to be covered with a covering sheet. In this case, the covering sheet is required to have weather resistance. In particular, the covering sheet is required to have weather resistance, i.e., resistance to ultraviolet rays.

[0006] An object of the present disclosure is to provide a covering sheet that is weather resistant. [Means for solving the problem]

[0007] The covering sheet according to one embodiment of the present disclosure comprises: A coating sheet used to coat steel materials, The film includes a barrier layer, a design layer, and a weather-resistant layer, The maximum spectral transmittance in the wavelength range of 300 nm or more and 350 nm or less is 1.0% or less.

[0008] A steel structure according to an embodiment of the present disclosure includes: The steel material; and a cover sheet according to one embodiment of the present disclosure.

[0009] A method for correcting a steel structure according to an embodiment of the present disclosure includes: A process of performing base preparation for deteriorated parts of a steel structure; and covering the steel material of the steel structure, the base of which has been conditioned, with a covering sheet according to one embodiment of the present disclosure. Effect of the Invention

[0010] According to the present disclosure, a weather-resistant covering sheet can be provided. [Brief description of the drawings]

[0011] [Figure 1A] FIG. 1A is a diagram for explaining this embodiment, and is a cross-sectional view showing an example of a steel structure. [Figure 1B] FIG. 1B is a cross-sectional view showing another example of a steel structure. [Figure 1C] FIG. 1C is a cross-sectional view showing another example of a steel structure. [Figure 1D] FIG. 1D is a cross-sectional view showing an example of a steel material and an anticorrosive layer. [Figure 2A] FIG. 2A is a cross-sectional view showing an example of a covering sheet that can be included in the steel structure shown in FIG. 1A. [Figure 2B]FIG. 2B is a cross-sectional view showing an example of a covering sheet that can be assembled to the steel structure shown in FIG. 1B. [Figure 2C] FIG. 2C is a cross-sectional view showing another example of a covering sheet that can be assembled to the steel structure shown in FIG. 1A. [Diagram 3] FIG. 3 is a diagram for explaining a method for measuring the storage elastic modulus of the bonding layer. [Figure 4A] FIG. 4A is a diagram for explaining a method for repairing a steel structure. [Figure 4B] FIG. 4B is a diagram for explaining a method for repairing a steel structure. [Figure 4C] FIG. 4C is a diagram for explaining a method for repairing a steel structure. [Figure 4D] FIG. 4D is a diagram for explaining a method for repairing a steel structure. [Diagram 5] FIG. 5 is a cross-sectional view showing an example of a steel structure to be repaired. [Figure 6] FIG. 6 is a cross-sectional view showing an example of a modified covering sheet. [Figure 7] FIG. 7 is a plan view showing an example of a modified steel structure. [Figure 8] FIG. 8 is a cross-sectional view showing an example of a modified steel structure. [Figure 9A] FIG. 9A is a diagram for explaining a modified steel structure repair method. [Figure 9B] FIG. 9B is a diagram for explaining a modified steel structure repair method. [Figure 9C] FIG. 9C is a diagram for explaining a modified steel structure repair method. [Figure 9D] FIG. 9D is a diagram for explaining a modified steel structure repair method. [Figure 9E] FIG. 9E is a diagram for explaining a modified steel structure repair method. [Figure 9F] FIG. 9F is a diagram for explaining a modified steel structure repair method. [Figure 10] FIG. 10 is a cross-sectional view showing another example of a modified steel structure. [Figure 11]FIG. 11 is a cross-sectional view showing another example of a modified steel structure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] One embodiment of the present disclosure is as follows. <1> ~ <11> Regarding.

[0013] <1> A coating sheet used to coat steel materials, The film includes a barrier layer, a design layer, and a weather-resistant layer, A covering sheet having a maximum spectral transmittance of 1.0% or less in the wavelength range of 300 nm or more and 350 nm or less. <2> A first surface facing away from the steel material and a second surface facing the steel material, The distance between the barrier layer and the second surface is smaller than the distance between the design layer and the second surface. <1> The covering sheet according to claim 1. <3> Further comprising a substrate, a distance between the barrier layer and the second surface is smaller than a distance between the weather-resistant layer and the second surface, and is also smaller than a distance between the substrate and the second surface; <2> The covering sheet according to claim 1. <4> Further comprising a transparent resin layer, The barrier layer, the base material, the design layer, the transparent resin layer, and the weather-resistant layer are laminated in this order from the second surface to the first surface. <3> The covering sheet according to claim 1. <5> When an anticorrosive layer is formed on a surface of the steel material, the surface of the steel material on which the anticorrosive layer is formed is covered with the covering sheet, and a weather resistance test is performed for 408 hours, the color difference ΔE of the anticorrosive layer before and after the weather resistance test is 4 or less. <1> ~ <4> 13. The covering sheet according to any one of claims 1 to 12. <6> The water vapor permeability at a temperature of 40°C and a humidity of 90% is 3.0g / (m 2 1 day) or less, <1> ~ <5> 13. The covering sheet according to any one of claims 1 to 12. <7> The oxygen permeability at a temperature of 23°C and a humidity of 60% is 6.57 cm 3 / (m 2 1 day) or less, <1> ~ <6> 13. The covering sheet according to any one of claims 1 to 12. <8> The weather-resistant layer contains an ultraviolet absorbing agent and a light stabilizer. <1> ~ <7> 13. The covering sheet according to any one of claims 1 to 12. <9> A first surface facing away from the steel material and a second surface facing the steel material, The adhesive layer and the base material constituting the second surface are included in the order from the second surface to the first surface. <1> ~ <8> 13. The covering sheet according to any one of claims 1 to 12. <10> The design layer is a colored substrate. <1> ~ <9> 13. The covering sheet according to any one of claims 1 to 12. <11> The steel material; The above <1> ~ <10> A steel structure comprising the covering sheet according to any one of claims 1 to 5. <12> The steel structure has a repaired portion and a non-repaired portion, The covering sheet is positioned on at least a portion of the repaired portion, The design layer of the covering sheet is a colored base material that is colored in the same color as the non-repaired portion. <11> A steel structure as described in the above. <13> The repaired portion of the steel material is covered with a first colored coating film having the same color as the non-repaired portion and formed so as to cover the covering sheet. <12> A steel structure as described in the above. <14> The method further includes forming an anticorrosive layer on a surface of the portion of the steel material located in the repaired portion. <12> or <13> A steel structure as described in the above. <15> The coating material further includes a second colored coating film formed on the surface of the anticorrosive layer. <14> A steel structure as described in the above. <16> A process of performing base preparation for deteriorated parts of a steel structure; The above <1> ~ <10> and covering the steel material of the steel structure that has been subjected to base preparation with the covering sheet according to any one of claims 1 to 5. <17> The steel structure has the deteriorated portion and a non-deteriorated portion, The design layer of the covering sheet is a colored base material colored in the same color as the undeteriorated portion. <16> A method for repairing a steel structure according to claim 1. <18> The method further includes a step of forming a first colored coating film having the same color as the undeteriorated portion so as to cover the surface-prepared portion of the steel structure and the covering sheet. <17> A method for repairing a steel structure according to claim 1. <19> The method further comprises the step of forming an anti-rust layer on the surface of the surface-prepared portion of the steel structure. <17> or <18> A method for repairing a steel structure according to claim 1. <20> The method further comprises the step of forming a second colored coating film having the same color as the undeteriorated portion on the surface of the anticorrosive layer. <19> A method for repairing a steel structure according to claim 1. <21> The covering sheet further includes a bonding layer and a release film covering the bonding layer, The steel structure repair method further includes a step of peeling off the release film from the bonding layer, In the step of covering the steel material of the steel structure, the steel material having a base surface prepared by the covering sheet, the covering sheet is bonded to the steel material by using the bonding layer exposed by peeling off the release film from the bonding layer. <16> ~ <20> 2. A method for repairing a steel structure according to claim 1 . <22> The step of performing surface preparation on the deteriorated portion of the steel structure includes a step of performing one, two, or three types of cleaning treatment on the deteriorated portion. <16> ~ <21> 2. A method for repairing a steel structure according to claim 1 .

[0014] Hereinafter, an embodiment of the present disclosure will be described in detail. In the drawings accompanying this specification, the scale and the aspect ratio are appropriately changed and exaggerated from those of the actual objects for the sake of ease of understanding.

[0015] In this specification, terms such as "film," "sheet," and "plate" are not distinguished from one another solely on the basis of differences in name. For example, a "coated sheet" cannot be distinguished from a member called a coated film or a coated plate solely on the basis of differences in name.

[0016] 1A to 1C and 2A to 2C all show cross sections along the normal direction of the covering sheet. In this specification, the normal direction of a film-like (sheet-like, plate-like) member refers to a direction parallel to a normal or perpendicular line to the film surface (sheet surface, plate surface) of the target film-like (sheet-like, plate-like) member. The "film surface (sheet surface, plate surface)" refers to a surface that coincides with the target film-like (sheet-like, plate-like) member when the target film-like (sheet-like, plate-like) member is viewed overall and globally.

[0017] In this specification, multiple upper limit candidates and multiple lower limit candidates for a numerical range may be described in separate sentences. In this description, the numerical range may be formed by combining any one upper limit candidate and any one lower limit candidate. As an example, consider the description "Parameter B may be A1 or more, A2 or more, or A3 or more. Parameter B may be A4 or less, A5 or less, or A6 or less." In this example, the numerical range of parameter B may be A1 or more and A4 or less, A1 or more and A5 or less, A1 or more and A6 or less, A2 or more and A4 or less, A2 or more and A5 or less, A2 or more and A6 or less, A3 or more and A4 or less, A3 or more and A5 or less, or A3 or more and A6 or less.

[0018] <<<Steel structures>>> As shown in Figs. 1A to 1C, a steel structure 10 comprises a steel material 20 and a covering sheet 30. The covering sheet 30 is used to cover the steel material 20. The covering sheet 30 includes a first surface 31 and a second surface 32. The second surface 32 faces the steel material 20. The first surface 31 faces the side opposite to the steel material 20. The first surface 31 may constitute a surface 11 of the steel structure 10.

[0019] 1A includes a steel material 20 and a covering sheet 30 in this order in the lamination direction. The covering sheet 30 is directly bonded to the steel material 20. A second surface 32 of the covering sheet 30 is in contact with the steel material 20.

[0020] In the example shown in FIG. 1B, the steel structure 10 includes a steel material 20, a bonding layer 15, and a covering sheet 30, in this order in the stacking direction. The bonding layer 15 is located between the steel material 20 and the covering sheet 30 in the stacking direction. The bonding layer 15 is in contact with the steel material 20 and the covering sheet 30. The bonding layer 15 is bonded to the steel material 20 and the covering sheet 30. The steel structure 10 shown in FIG. 1B differs from the example shown in FIG. 1A in that it includes the bonding layer 15. The steel structure 10 shown in FIG. 1B may otherwise be configured similarly to the steel structure 10 shown in FIG. 1A.

[0021] In the example shown in Fig. 1C, the steel structure 10 includes a steel material 20, an anti-corrosion layer 18, a bonding layer 15, and a covering sheet 30 in this order in the lamination direction. The anti-corrosion layer 18 is located between the steel material 20 and the bonding layer 15 in the lamination direction. The anti-corrosion layer 18 is in contact with the steel material 20 and the bonding layer 15. The steel structure 10 shown in Fig. 1C differs from the example shown in Fig. 1B in that it includes the anti-corrosion layer 18. The steel structure 10 shown in Fig. 1C may otherwise be configured similarly to the steel structure 10 shown in Fig. 1B.

[0022] In the example shown in FIG. 1C, the bonding layer 15 may be omitted. Alternatively, the steel structure 10 shown in FIG. 1A may include the rust-preventive layer 18 shown in FIG. 1C. The steel structure 10 may include an additional layer, without being limited to the examples shown in FIG. 1A to FIG. 1C. As an example, as shown by a two-dot chain line in FIG. 1C, the steel structure 10 may include a topcoat layer 19 constituting the outermost layer. In this example, the covering sheet 30 may be located between the topcoat layer 19 and the steel material 20 in the lamination direction. The topcoat layer 19 may have one or more functions expected of the outermost layer, such as barrier properties, weather resistance, scratch resistance, strength, etc.

[0023] The steel structure 10 is a structure including a steel material 20. The steel material 20 may constitute the base material of the steel structure 10. Examples of the steel structure 10 include a bridge, a bridge pier, a steel tower, a steel pipe, a chimney, a tank, a plant, a pipeline, a rolled plate, and a roof. The steel structure may be, for example, an architectural structure or a civil engineering structure.

[0024] Examples of the steel material 20 include alloy steels such as nickel-chromium steel, nickel-chromium-molybdenum steel, chromium steel, chromium-molybdenum steel, and manganese steel, as well as carbon steel. The steel material 20 may corrode due to corrosion factors such as water and oxygen. The steel material 20 may include a rusted portion on the surface where rust has occurred due to corrosion. An example of the rust is red rust such as iron oxide (Fe2O3). The portion of the steel material 20 where an abnormality has occurred, such as the rusted portion, constitutes the deteriorated portion 12 of the steel structure 10.

[0025] The steel structure 10 may include a coating film that covers the steel material 20. The coating film may be provided for the purpose of suppressing deterioration of the steel material 20. An example of the coating film is the anti-corrosive layer 18 shown in FIG. 1C. The coating film may develop defects such as cracks and blisters due to deterioration over time or construction or repair work performed on the steel structure. Parts of the coating film where defects such as cracks and blisters have occurred also constitute deteriorated parts 12 of the steel structure.

[0026] The covering sheet 30 is used to cover the steel material 20. The covering sheet 30 may protect the steel material 20 by covering the steel material 20. The covering sheet 30 may suppress deterioration of the steel material 20. The covering sheet 30 may be laminated on the steel material 20 when the steel structure 10 is newly constructed. The covering sheet 30 may be used to repair the steel structure 10 having a deteriorated portion 12. The covering sheet 30 used for repair may be laminated on a portion of the steel structure 10 from which the deteriorated portion 12 has been removed.

[0027] According to a steel structure 10 including steel materials 20 and a covering sheet 30, deterioration of the covering sheet 30 can be suppressed by the action of the covering sheet 30 described below. Furthermore, the covering sheet 30 can protect the parts of the steel structure 10 other than the covering sheet 30, such as the steel materials 20 and the coating film formed on the steel materials 20, which are covered by the covering sheet 30. This can suppress deterioration of the parts. For example, the covering sheet 30 can protect the steel materials 20 and the parts of the coating film formed on the steel materials 20 that are covered by the covering sheet 30 from ultraviolet rays. This can suppress deterioration of the steel materials 20 and the coating film formed on the steel materials 20 due to ultraviolet rays.

[0028] <<<Covering sheet>>> The cover sheet 30 according to this embodiment has a maximum spectral transmittance of 1.0% or less in the wavelength range of 300 nm or more and 350 nm or less.

[0029] The covering sheet 30 having a maximum spectral transmittance of 1.0% or less in the wavelength range of 300 nm or more and 350 nm or less can suppress deterioration of the covering sheet 30. The covering sheet 30 is intended to be installed outdoors. The covering sheet 30 having a maximum spectral transmittance of 1.0% or less in the wavelength range of 300 nm or more and 350 nm or less can suppress deterioration due to strong ultraviolet rays contained in sunlight.

[0030] As described above, by setting an upper limit on the spectral transmittance in the ultraviolet wavelength range of 300 nm or more and 350 nm or less, it is possible to provide the covering sheet 30 that is weather resistant, in particular resistant to ultraviolet light. The spectral transmittance in the ultraviolet wavelength range is an index of weather resistance.

[0031] The maximum spectral transmittance at wavelengths of 300 nm or more and 350 nm or less may be 1.0% or less, or 0.50% or less. Such a covering sheet 30 can effectively suppress ultraviolet degradation in outdoor installation applications. The covering sheet 30 can protect the steel material 20 and the coating film for a long period of time.

[0032] There is no particular lower limit for the maximum transmittance at a wavelength of 300 nm or more and 350 nm or less through the cover sheet 30. The maximum transmittance at a wavelength of 300 nm or more and 350 nm or less through the cover sheet 30 may be 0% or more, or may be greater than 0%.

[0033] The transmittance at each wavelength, i.e., the spectral transmittance, is the arithmetic mean value of five measured values ​​measured according to JIS Z8722:2009. The five measured values ​​are measured at five measurement positions on a sample of the covering sheet 30 to be evaluated. The five measurement positions are located 10 mm or more apart from each other.

[0034] The measurement wavelengths for spectral transmittance are in the range of 300 nm to 350 nm, with 1 nm intervals. In other words, the spectral transmittance is measured for light with integer wavelengths (nm) between 300 nm and 350 nm. The geometric condition f specified in JIS Z8722:2009 is used in the measurement of spectral transmittance.

[0035] The incident angle on the sample when measuring the spectral transmittance is 0°. The incident surface when measuring the spectral transmittance is the first surface 31 of the cover sheet 30.

[0036] The test environment for measuring the spectral transmittance is 23℃±2℃ and 50%±5% relative humidity. The sample is placed in the test environment for 16 hours before the start of the test. Before measuring the spectral transmittance, the light source of the measuring device is turned on for 15 minutes to stabilize the output of the light source.

[0037] The covering sheet 30 according to the present embodiment may have the following characteristics: An anticorrosive layer 18 is formed on a surface of a steel material 20, the surface of the steel material 20 on which the anticorrosive layer 18 is formed is covered with a covering sheet 30, and a weather resistance test is performed for 408 hours. In this case, the color difference ΔE of the anticorrosive layer 18 before and after the weather resistance test is 4 or less.

[0038] The method for measuring the color difference ΔE of the anticorrosive layer 18 before and after the weather resistance test will be described in detail. First, a steel material 20 on which the anticorrosive layer 18 is formed is prepared as shown in FIG. 1D. The material of the anticorrosive layer 18 is Sabishut manufactured by Dai Nippon Toryo Co., Ltd. Next, the covering sheet 30 to be measured and the anticorrosive layer 18 are bonded. At this time, the covering sheet 30 and the anticorrosive layer 18 are bonded so that the surface of the anticorrosive layer 18 and the second surface 32 of the covering sheet 30 face each other. When the second surface 32 of the covering sheet 30 is constituted by the bonding layer 15, the covering sheet 30 and the anticorrosive layer 18 are bonded using the bonding layer 15. When the second surface 32 of the covering sheet 30 is not constituted by the bonding layer 15, the covering sheet 30 and the anticorrosive layer 18 are bonded via an acrylic adhesive. In this case, the thickness of the acrylic adhesive layer can be 80 μm.

[0039] Next, a 408-hour weathering test is performed on the covering sheet 30 bonded to the rust-preventive layer 18 formed on the steel material 20. The 408-hour weathering test is performed as follows. The weathering test is performed using a weathering test device. The covering sheet 30 to be evaluated is subjected to a cycle of a 20-hour irradiation step and a 4-hour condensation step, which is repeated until 408 hours are reached. A 30-second shower step is performed after the irradiation step and before the condensation step is started, and after the condensation step and before the irradiation step is started. In the shower step, the sample held in the weathering test device is exposed to a water shower.

[0040] The weather resistance test equipment used is the ultra-accelerated weather resistance test equipment "Eye Super UV Tester SUV-W261" manufactured by Iwasaki Electric Co., Ltd. The UV lamp, lamp jacket, and illuminometer included in the weather resistance test equipment are as follows. UV lamp: Product name: M04-L21WB / SUV, manufactured by Iwasaki Electric Co., Ltd. Lamp jacket: Product name: WJ50-SUV, manufactured by Iwasaki Electric Co., Ltd. Illuminance meter: Product name: UVD-365PD, manufactured by Iwasaki Electric Co., Ltd.

[0041] The conditions for the irradiation step are as follows: <Irradiation conditions> Black panel temperature: 63℃ ·Illuminance: 100mW / cm 2 ·Battle humidity: 50%RH Duration: 20 hours

[0042] The conditions for the condensation process are as follows: <Condensation conditions> ·Illuminance: 0mW / cm 2 ·Battle humidity: 98%RH Duration: 4 hours

[0043] Then, the color difference ΔE of the anticorrosive layer 18 is measured before and after the weather resistance test. The measured color difference ΔE is L * a* b * In the color system, the color before the weather resistance test is L * 1a * 1b * 1. The color after weather resistance test * 2a * 2b * 2, which is defined by the following equations (1) to (4).

number

[0044] Color L before weather resistance test * 1a * 1b * 1, and color L after weather resistance test * 2a * 2b * 2 is the color of the anticorrosive layer 18 when observed through the covering sheet 30 from the first surface 31 side of the covering sheet 30.

[0045] The effect of the covering sheet 30 having a color difference ΔE of 4 or less measured as described above will be described. As described above, the covering sheet 30 may be required to have resistance to ultraviolet rays. In particular, it is preferable that the covering sheet 30 can suppress deterioration of the materials contained in the covering sheet 30 due to ultraviolet rays. In this case, it is particularly preferable that the covering sheet 30 has resistance to ultraviolet rays.

[0046] The covering sheet 30 having a color difference ΔE of 4 or less measured as described above can protect the anticorrosive layer 18 from ultraviolet rays when the covering sheet 30 covers the anticorrosive layer 18 as shown in FIG. 4D. This can prevent the material contained in the anticorrosive layer 18 from being altered by ultraviolet rays. In particular, the covering sheet 30 having a color difference ΔE of 4 or less can prevent the anticorrosive layer 18 from being discolored by ultraviolet rays. In this case, the covering sheet 30 having a color difference ΔE of 4 or less may prevent the anticorrosive layer 18 from being yellowed by ultraviolet rays.

[0047] <<Layer structure of the covering sheet>> The covering sheet 30 according to the present embodiment includes a barrier layer 44, a design layer 47, and a weather-resistant layer 42. In the example shown in FIG. 2A, the covering sheet 30 further includes a substrate 41. In the example shown in FIG. 2A, the covering sheet 30 further includes a transparent resin layer 48. In the example shown in FIG. 2A, the covering sheet 30 further includes an adhesive layer 43 constituting the second surface 32 of the covering sheet 30. In the example shown in FIG. 2A, the covering sheet 30 further includes an adhesive layer 491 that bonds the barrier layer 44 and the substrate 41, and an adhesive layer 492 that bonds the design layer 47 and the transparent resin layer 48. Although not shown, the adhesive layer 491 and the adhesive layer 492 may be omitted.

[0048] 2A , the distance w6 between the barrier layer 44 and the second surface 32 is smaller than the distance w7 between the design layer 47 and the second surface 32. That is, the barrier layer 44 and the design layer 47 are laminated in this order from the second surface 32 toward the first surface 31. Because the distance w6 is smaller than the distance w7, the design layer 47 can reduce the amount of ultraviolet light that is irradiated onto the first surface 31 of the covering sheet 30 and reaches the barrier layer 44. This makes it possible to suppress deterioration of the barrier layer 44 due to ultraviolet light, and maintain the gas barrier properties of the barrier layer 44.

[0049] In the example shown in FIG. 2A, the distance w6 between the barrier layer 44 and the second surface 32 is smaller than the distance w8 between the weather-resistant layer 42 and the second surface 32, and is smaller than the distance w9 between the substrate 41 and the second surface 32. That is, when the positional relationship between the barrier layer 44 and the weather-resistant layer 42 is considered, the barrier layer 44 and the weather-resistant layer 42 are laminated in the order from the second surface 32 to the first surface 31. When the positional relationship between the barrier layer 44 and the substrate 41 is considered, the barrier layer 44 and the substrate 41 are laminated in the order from the second surface 32 to the first surface 31. Since the distance w6 is smaller than the distance w8, the weather-resistant layer 42 can reduce the ultraviolet light irradiated to the first surface 31 of the covering sheet 30 and reaching the barrier layer 44. This can suppress the deterioration of the barrier layer 44 due to the ultraviolet light, and maintain the gas barrier property of the barrier layer 44. When the distance w6 is smaller than the distance w9, the ultraviolet light that is irradiated onto the first surface 31 of the covering sheet 30 and reaches the barrier layer 44 can be reduced by the base material 41. This makes it possible to suppress deterioration of the barrier layer 44 due to the ultraviolet light and maintain the gas barrier property of the barrier layer 44.

[0050] 2A, the covering sheet 30 includes, in the order from the second surface 32 to the first surface 31, an adhesive layer 43 constituting the second surface 32, and a substrate 41. This allows the covering sheet 30 to be bonded to the steel material 20 or a coating film on the steel material 20 by the adhesive layer 43, as described below.

[0051] In the covering sheet 30, the barrier layer 44, the substrate 41, the design layer 47, the transparent resin layer 48, and the weather-resistant layer 42 may be laminated in this order from the second surface 32 to the first surface 31 in the lamination direction. In this case, the substrate 41, the design layer 47, the transparent resin layer 48, and the weather-resistant layer 42 can reduce ultraviolet rays that are irradiated to the first surface 31 of the covering sheet 30 and reach the barrier layer 44. This can more stably suppress the deterioration of the barrier layer 44 due to ultraviolet rays, and more stably maintain the gas barrier property of the barrier layer 44. In the example shown in FIG. 2A, the bonding layer 43, the barrier layer 44, the bonding layer 491, the substrate 41, the design layer 47, the bonding layer 492, the transparent resin layer 48, and the weather-resistant layer 42 are laminated in this order from the second surface 32 to the first surface 31 in the lamination direction. The covering sheet 30 shown in FIG. 2A can be included in the steel structure 10 shown in FIG. 1A. 2A, the weathering layer 42 constitutes the first surface 31. As described above, the bonding layer 43 constitutes the second surface 32. The bonding layer 43 is in contact with the steel material 20. The bonding layer 43 may be bonded to the steel material 20.

[0052] As shown in FIG. 2B, the bonding layer 43 may be omitted. The covering sheet 30 shown in FIG. 2B may be included in the steel structure 10 shown in FIG. 1A. The covering sheet 30 shown in FIG. 2B may be included in the steel structure 10 shown in FIG. 1B and FIG. 1C. In the example shown in FIG. 1B and FIG. 1C, the covering sheet 30 is bonded to the steel material 20 by the bonding layer 15. The covering sheet 30 may be welded to the steel material 20 without using a bonding layer. When the bonding layer 43 is omitted, the barrier layer 44 may constitute the second surface 32 of the covering sheet 30, although not shown. When the barrier layer 44 constitutes the second surface 32, the distance w6 between the barrier layer 44 and the second surface 32 is 0.

[0053] Each layer that may be included in the cover sheet 30 will now be described in further detail.

[0054] <Base material> The substrate 41 may be a resin film. Examples of resin materials constituting the substrate 41 include polyolefins such as polyethylene and polypropylene, polyvinyl chloride, vinylidene chloride-vinyl chloride copolymers, polyesters such as polyethylene terephthalate, polycarbonates, polyarylates, styrene resins, acrylic resins, acrylic urethane resins, urethane resins, fluororesins, acetyl cellulose, polyamides, and polyimides. The substrate 41 may be a single layer or a multilayer. The substrate 41 may be a laminated film of resin films.

[0055] In one embodiment, the substrate 41 includes a polyolefin, such as polyethylene, polypropylene, polybutene, and polymethylpentene. In one embodiment, the substrate 41 includes a polypropylene.

[0056] Examples of polypropylene include propylene homopolymers, ethylene-propylene copolymers, propylene-butene copolymers, and ethylene-propylene-butene copolymers. Among these, propylene homopolymers, ethylene-propylene copolymers, and propylene-butene copolymers are preferred.

[0057] From the viewpoint of processability, the polyolefin content of the substrate 41 is preferably 50% by mass or more, more preferably 60% by mass or more, even more preferably 70% by mass or more, and particularly preferably 80% by mass or more, based on the total resin components of the substrate 41.

[0058] The substrate 41 may contain additives. Examples of additives include wear resistance improvers, infrared absorbers, antistatic agents, fillers, foaming agents, flame retardants, mildew inhibitors, plasticizers, leveling agents, flow control agents, defoamers, dispersants, antisettling agents, lubricants, and colorants. The substrate 41 may contain weathering agents such as ultraviolet absorbers, antioxidants, and light stabilizers. The substrate 41 containing the weathering agents has excellent weather resistance. In the covering sheet 30 in which the substrate 41 has weather resistance, the overcoat layer described below may be thinned, or the overcoat layer may be omitted. Examples of ultraviolet absorbers include benzotriazole-based ultraviolet absorbers, benzophenone-based ultraviolet absorbers, triazine-based ultraviolet absorbers, and hydroxyphenyltriazine-based ultraviolet absorbers. Examples of light stabilizers include hindered amine-based light stabilizers such as piperidinyl sebacate-based light stabilizers. Examples of colorants include dyes and pigments.

[0059] The substrate 41 may be colorless and transparent, or may contain colorants such as dyes and pigments, as described above with respect to the additives. For example, when the surface hue of the adherend to which the covering sheet 30 is applied varies, and it is desired to conceal the surface hue and improve the stability of the color tone of the design layer, the substrate 41 may contain an inorganic pigment such as a white pigment.

[0060] Examples of pigments include white pigments such as zinc oxide, white lead, lithopone, titanium dioxide, precipitated barium sulfate, and baryte; black pigments such as carbon black; red pigments such as red lead and red iron oxide; yellow pigments such as yellow lead and zinc yellow (zinc yellow type 1, zinc yellow type 2); and blue pigments such as ultramarine blue and Prussian blue (potassium ferrocyanide).

[0061] The content of the colorant may be 1 part by mass or more, 3 parts by mass or more, 5 parts by mass or more, 50 parts by mass or less, 40 parts by mass or less, or 30 parts by mass or less, relative to 100 parts by mass of the polyolefin contained in the base layer.

[0062] From the viewpoint of a balance between design and processability, the thickness of the substrate 41 is preferably 20 μm or more, more preferably 25 μm or more, and even more preferably 30 μm or more. From the viewpoint of a balance between design and processability, the thickness of the substrate 41 is preferably 150 μm or less, more preferably 120 μm or less, and even more preferably 100 μm or less.

[0063] One or both sides of the substrate 41 may be subjected to a surface treatment. Examples of the surface treatment include physical surface treatments such as oxidation and roughening, and chemical surface treatments. Examples of the oxidation method include corona discharge treatment, chromium oxidation treatment, flame treatment, hot air treatment, and ozone-ultraviolet treatment. Examples of the roughening method include sandblasting and solvent treatment. The substrate layer may have an easy-adhesion layer on one or both sides. This can improve, for example, the interlayer adhesion between the substrate layer and other layers.

[0064] The substrate 41 may have a bubble structure (cell structure). The bubble structure (cell structure) may be a closed cell structure, an open cell structure, or a semi-open and semi-closed cell structure in which a closed cell structure and an open cell structure are mixed. An example of the substrate 41 having a bubble structure is a foam layer. More specifically, an example of the substrate 41 is an acrylic resin foam (acrylic foam), a urethane resin foam (urethane foam), a polyolefin foam, and a rubber foam containing an acrylic rubber and other elastomers.

[0065] The thickness of the substrate 41 may be determined in consideration of the finish after repair of the steel structure, i.e., the finish after the covering sheet 30 is applied to the steel material 20, the handling and ease of application of the covering sheet 30, etc. The thickness of the substrate 41 may be 10 μm or more, 20 μm or more, 30 μm or more, 50 μm or more, or 100 μm or more. The thickness of the substrate 41 may be 5000 μm or less, 4000 μm or less, 3000 μm or less, 2000 μm or less, or 1000 μm or less.

[0066] The substrate 41 may include a fiber-reinforced resin layer. The fiber-reinforced resin layer can improve the impact resistance of the substrate 41 and the covering sheet 30. The fiber-reinforced resin layer may include a resin material and reinforcing fibers. Examples of the resin material include the resin materials that can be used for the substrate 41 described above. The reinforcing fibers may be inorganic fibers or organic fibers. Examples of the inorganic fibers include glass fibers, carbon fibers, silicon-titanium-carbon fibers, boron fibers, and metal fibers. Examples of the organic fibers include aramid fibers, vinylon fibers, polyester fibers, and polyamide fibers. The reinforcing fibers may be in a mesh (network) shape. The fiber-reinforced resin layer may include a glass mesh as a reinforcing fiber.

[0067] The thickness of the fiber reinforced resin layer may be 50 μm or more, 75 μm or more, 100 μm or more, 125 μm or more, or 150 μm or more. The thickness of the fiber reinforced resin layer may be 550 μm or less, 525 μm or less, 500 μm or less, 475 μm or less, or 450 μm or less. By setting the thickness of the fiber reinforced resin layer in this manner, impact resistance can be imparted to the covering sheet 30.

[0068] The substrate 41 may include a laminate including a fiber-reinforced resin layer and a resin layer. The substrate 41 may include a laminate including a first resin layer, a fiber-reinforced resin layer, and a second resin layer. Examples of resin materials constituting the resin layer, the first resin layer, and the second resin layer include the resin materials that can be used for the substrate 41 described above. The laminate included in the substrate 41 may include a fiber-reinforced resin layer including polyethylene and a glass net, and a polyethylene layer. The laminate included in the substrate 41 may include a first polyethylene layer, a fiber-reinforced resin layer including polyethylene and a glass net, and a second polyethylene layer.

[0069] The thickness of the resin layer, the thickness of the first resin layer, and the thickness of the second resin layer may each be 10 μm or more, 20 μm or more, 30 μm or more, 50 μm or more, or 100 μm or more. The thickness of the resin layer, the thickness of the first resin layer, and the thickness of the second resin layer may each be 1000 μm or less, 800 μm or less, 600 μm or less, 500 μm or less, or 400 μm or less.

[0070] <Weatherproof layer> The weather-resistant layer 42 is a layer having weather resistance. The weather-resistant layer 42 may contain a binder resin and a weather-resistant agent. The weather-resistant layer 42 may contain, as the weather-resistant agent, one or more of an ultraviolet absorbing agent, an antioxidant, and a light stabilizer. The weather-resistant layer 42 may contain an ultraviolet absorbing agent and a light stabilizer.

[0071] The weather-resistant layer 42 may contain a cured resin as a binder resin. The cured resin is a cured product of a curable resin composition. The curable resin composition may be a thermosetting resin composition. The curable resin composition may be an ionizing radiation curable resin composition. The weather-resistant layer 42 may contain a cured product of a curable resin composition and a cured product of an ionizing radiation curable resin composition.

[0072] The thermosetting resin composition includes a thermosetting resin. The thermosetting resin composition is cured by heating. Examples of the thermosetting resin include unsaturated group-containing (meth)acrylic resin, unsaturated polyester, urethane resin, epoxy resin, phenol resin, aminoalkyd resin, urea resin, melamine resin, melamine-urea co-condensation resin, guanamine resin, diallyl phthalate resin, and silicone resin.

[0073] The thermosetting resin composition may contain a curing agent together with the thermosetting resin. In the case of an unsaturated group-containing (meth)acrylic resin and an unsaturated polyester, a peroxide such as methyl ethyl ketone peroxide or a radical initiator such as azoisobutylnitrile may be used. In the case of a urethane resin, an isocyanate-based curing agent may be used. In the case of an epoxy resin, an organic amine-based curing agent may be used.

[0074] The thermosetting resin may be a two-component curing urethane resin that uses a polyol as a base and an isocyanate compound as a curing agent. Examples of polyols include (meth)acrylic polyols, polyether polyols, polyester polyols, polyethylene glycols, and polypropylene glycols. The isocyanate compound is a polyvalent isocyanate having two or more isocyanate groups. Examples of the isocyanate compound include aromatic isocyanates such as 4,4-diphenylmethane diisocyanate; and aliphatic (or alicyclic) isocyanates such as hexamethylene diisocyanate, isophorone diisocyanate, hydrogenated tolylene diisocyanate, and hydrogenated diphenylmethane diisocyanate.

[0075] In one specific example of the weather-resistant layer 42, the cured resin contained in the weather-resistant layer 42 may be a crosslinked cured product of a (meth)acrylic polyol with an isocyanate-based curing agent.

[0076] The ionizing radiation curable resin composition contains a compound having an ionizing radiation curable functional group. Hereinafter, the compound having an ionizing radiation curable functional group is also referred to as an "ionizing radiation curable compound". The ionizing radiation curable functional group is a group that crosslinks when irradiated with ionizing radiation.

[0077] The ionizing radiation may be electromagnetic waves or charged particle beams. The ionizing radiation has an energy quantum capable of polymerizing or crosslinking molecules. Examples of the ionizing radiation include ultraviolet (UV) rays, electron beams (EB), X-rays, gamma rays, alpha rays, and ion beams. In an example in which the weather-resistant layer 42 contains an ultraviolet absorbing agent as a weather-resistant agent, the ionizing radiation may be an electron beam.

[0078] Examples of the ionizing radiation curable functional group include ethylenically unsaturated bond groups such as (meth)acryloyl group, vinyl group, and allyl group, as well as epoxy group and oxetanyl group. The ionizing radiation curable compound may contain an ethylenically unsaturated bond group. The ionizing radiation curable compound may contain two or more ethylenically unsaturated bond groups. The ionizing radiation curable compound may be a polyfunctional (meth)acrylate compound containing two or more ethylenically unsaturated bond groups. The polyfunctional (meth)acrylate compound may contain either a monomer or an oligomer.

[0079] Examples of the polymerizable monomer include a (meth)acrylate monomer having a (meth)acryloyl group in the molecule and a polyfunctional (meth)acrylate monomer having two or more (meth)acryloyl groups in the molecule. The number of (meth)acryloyl groups in the polyfunctional (meth)acrylate monomer may be 2 or more and 8 or less, or 2 or more and 6 or less.

[0080] Examples of the polymerizable monomer include bifunctional (meth)acrylates such as ethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, bisphenol A tetraethoxy di(meth)acrylate, and bisphenol A tetrapropoxy di(meth)acrylate; trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tri(meth)acrylate, and the like. Examples include tri- or higher functional (meth)acrylates such as erythritol tetra(meth)acrylate, dipentaerythritol tri(meth)acrylate, dipentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, and dipentaerythritol hexa(meth)acrylate; and ethylene oxide-, propylene oxide-, caprolactone-, isocyanuric acid-, or propionic acid-modified products of these (meth)acrylates.

[0081] Examples of the polymerizable oligomer include (meth)acrylate oligomers having two or more (meth)acryloyl groups in the molecule. Examples of the (meth)acrylate oligomer include urethane (meth)acrylate, epoxy (meth)acrylate, polyester (meth)acrylate, polyether (meth)acrylate, polycarbonate (meth)acrylate, polycaprolactone urethane (meth)acrylate, polycaprolactone diol urethane (meth)acrylate, and acrylic (meth)acrylate. The number of (meth)acryloyl groups in the polymerizable oligomer may be 2 or more and 8 or less, or 2 or more and 6 or less.

[0082] Examples of the polymerizable oligomer include highly hydrophobic polybutadiene (meth)acrylate oligomers having (meth)acryloyl groups in the side chains of polybutadiene oligomers, and silicone (meth)acrylate oligomers having polysiloxane bonds in the main chains.

[0083] The weight average molecular weight of the polymerizable oligomer may be 500 or more, 1,000 or more, or 2,000 or more. The weight average molecular weight of the polymerizable oligomer may be 10,000 or less, 8,000 or less, or 6,000 or less. The weight average molecular weight is an average molecular weight measured by gel permeation chromatography (GPC) analysis and converted into standard polystyrene.

[0084] As the ionizing radiation curable compound, a monofunctional (meth)acrylate may be used together with a polyfunctional (meth)acrylate. This can reduce the viscosity of the curable composition during application. Examples of the monofunctional (meth)acrylate include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, cyclohexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate, and isobornyl (meth)acrylate.

[0085] When the ionizing radiation curable compound is an ultraviolet ray curable compound, at least one selected from a photopolymerization initiator and a photopolymerization accelerator may be used together with the ultraviolet ray curable compound.

[0086] From the viewpoint of excellent heat resistance, scratch resistance, and contamination resistance, the weather-resistant layer 42 may contain a cured product of a curable compound or a cured product of an ionizing radiation curable composition. A coating liquid containing an electron beam curable compound can be made solvent-free and does not require a photopolymerization initiator. The electron beam curable compound can obtain stable curing characteristics. In addition, the electron beam curable compound can stably hold additives such as weather resistance agents, for example, ultraviolet absorbers, by crosslinking. Therefore, the bleed-out of additives such as ultraviolet absorbers can be stably suppressed. This makes it possible to suppress deterioration of the excellent weather resistance of the weather-resistant layer 42 over time. From the above, the weather-resistant layer 42 preferably contains a cured product of an electron beam curable compound. The ionizing radiation curable compound may be a polymerizable oligomer, a (meth)acrylate oligomer having two or more (meth)acryloyl groups in the molecule, or a urethane (meth)acrylate.

[0087] The content of the cured resin relative to all resin components contained in the weather-resistant layer 42 may be 50 mass % or more, 70 mass % or more, 80 mass % or more, or 90 mass % or more.

[0088] The weather-resistant layer 42 can be produced by forming a coating film of a coating liquid containing a curable resin composition and curing the coating film. In an example in which the weather-resistant layer 42 contains a cured product of an electron beam curable resin composition, the coating film is irradiated with electron beams. A portion of the electron beams penetrates the coating film and is also irradiated to the substrate 41. In this example, the substrate 41 may contain a polyolefin. The polyolefin is crosslinked to some extent by the electron beam. The crosslinking of the polyolefin improves the heat resistance of the substrate 41.

[0089] The substrate 41 containing polyolefin can improve adhesion to the weather-resistant layer 42 containing a cured product of an electron beam curable resin composition, compared to a substrate containing a fluororesin. Furthermore, by using polyolefin instead of a fluororesin for the substrate 41, it is possible to suppress the generation of PFAS as an impurity. As an artificial organic fluorine compound, PFAS is a concern due to its bioaccumulation. Suppressing the generation of PFAS can contribute to reducing the environmental load.

[0090] In view of the above, the substrate 41 may contain a polyolefin in combination with the weather-resistant layer 42 containing the cured product of the electron beam curable resin composition. Examples of polyolefins used in the substrate 41 include polyethylene, polypropylene, polybutene, and polymethylpentene.

[0091] Examples of polypropylene include propylene homopolymers, ethylene-propylene copolymers, propylene-butene copolymers, and copolymers such as ethylene-propylene-butene copolymers. As the polypropylene contained in the base material 41, propylene homopolymers, ethylene-propylene copolymers, and propylene-butene copolymers are preferred.

[0092] From the viewpoint of processability, the content of polyolefin in the substrate 41 may be 50% by mass or more, 60% by mass or more, 70% by mass or more, or 80% by mass or more, based on the total resin components of the substrate 41.

[0093] <Transparent resin layer> The transparent resin layer 48 has a transparency sufficient to allow an observer observing the first surface 31 of the covering sheet 30 to visually recognize the design displayed on the design layer 47. The transparent resin layer 48 is located between the design layer 47 and the weather-resistant layer 42. The material of the transparent resin layer 48 is not particularly limited as long as it can ensure a transparency sufficient to allow an observer to visually recognize the design displayed on the design layer 47. Examples of materials for the transparent resin layer 48 include polyolefins such as polyethylene and polypropylene, polyvinyl chloride, vinylidene chloride-vinyl chloride copolymers, polyesters such as polyethylene terephthalate, polycarbonates, polyarylates, styrene resins, acrylic resins, acrylic urethane resins, urethane resins, fluororesins, acetyl cellulose, polyamides, and polyimides.

[0094] As an example, the transparent resin layer 48 contains a polyolefin, for example, polyethylene, polypropylene, polybutene, and polymethylpentene.

[0095] In one embodiment, the transparent resin layer 48 contains polypropylene. The polyolefin contained in the transparent resin layer 48 and the polyolefin contained in the base material 41 may be the same or different. Examples of polypropylene include copolymers such as a propylene homopolymer, an ethylene-propylene copolymer, a propylene-butene copolymer, and an ethylene-propylene-butene copolymer. Among these, a propylene homopolymer, an ethylene-propylene copolymer, and a propylene-butene copolymer are preferred. From the viewpoint of processability, the content of the polyolefin in the transparent resin layer 48 is preferably 50% by mass or more, more preferably 60% by mass or more, even more preferably 70% by mass or more, and particularly preferably 80% by mass or more, based on the total resin components of the transparent resin layer 48.

[0096] The transparent resin layer 48 may contain additives. Examples of additives include pigments, dyes, dispersants, defoamers, thickeners, leveling agents, anti-settling agents, anti-sagging agents, anti-algae agents, anti-fungal agents, preservatives, ultraviolet absorbers, antioxidants, and light stabilizers. In particular, the transparent resin layer 48 may contain weathering agents such as ultraviolet absorbers, antioxidants, and light stabilizers. This can increase the weather resistance of the transparent resin layer 48 and the part of the steel structure 10 covered by the transparent resin layer 48. When the transparent resin layer 48 contains an ultraviolet absorber, the ultraviolet absorber contained in the transparent resin layer 48 is, for example, the ultraviolet absorber described above as the ultraviolet absorber contained in the base material 41. It is an ultraviolet absorber. The light stabilizer contained in the transparent resin layer 48 is, for example, the light stabilizer described above as the light stabilizer contained in the base material 41. The transparent resin layer 48 may contain additives other than the ultraviolet absorbers and light stabilizers described above as the additives contained in the base material 41.

[0097] The content of the ultraviolet absorber in the transparent resin layer 48 may be 0.05 parts by mass or more, 0.10 parts by mass or more, 10 parts by mass or less, or 5 parts by mass or less, relative to 100 parts by mass of the polyolefin contained in the transparent resin layer 48.

[0098] The content of the light stabilizer in the transparent resin layer 48 may be 0.1 parts by mass or more, 0.5 parts by mass or more, 10 parts by mass or less, or 8 parts by mass or less, relative to 100 parts by mass of the polyolefin contained in the transparent resin layer 48.

[0099] The transparent resin layer 48 may be transparent to such an extent that the substrate 41 side from the transparent resin layer 48 can be visually recognized, and may be colorless and transparent, colored and transparent, or translucent.

[0100] The thickness of the transparent resin layer 48 may be 10 μm or more, 20 μm or more, 30 μm or more, 40 μm or more, 50 μm or more, or 60 μm or more from the viewpoint of balance of scratch resistance, processing suitability, and weather resistance. The thickness of the transparent resin layer 48 may be 1000 μm or less, 800 μm or less, 600 μm or less, 500 μm or less, 400 μm or less, 150 μm or less, 120 μm or less, or 100 μm or less from the viewpoint of balance of scratch resistance, processing suitability, and weather resistance. The thickness of the transparent resin layer 48 is preferably larger than the thickness of the substrate 41 from the viewpoint of protecting the design layer 47 and obtaining excellent scratch resistance.

[0101] <Design layer> The design layer 47 is a layer that imparts a desired design to the covering sheet 30. In this embodiment, the design layer 47 is provided on the substrate 41. In other words, in this embodiment, the covering sheet 30 has the design layer 47 superimposed on the substrate 41 in the thickness direction of the covering sheet 30. The substrate 41 and the design layer 47 may be in contact with each other, or another layer may be present between the substrate 41 and the design layer 47.

[0102] The design layer 47 is provided to display the design expressed by the covering sheet 30. The design layer 47 imparts a desired design to the covering sheet 30 so that it can be visually recognized by an observer who observes the first surface 31 of the covering sheet 30. The design layer 47 may impart a desired design to the entire surface of the first surface 31 of the covering sheet 30. The design layer 47 may impart a desired design to a part of the first surface 31 of the covering sheet 30. The design layer 47 may have a single color. The design layer 47 may be composed of multiple colors. The design layer 47 may display symbols such as letters and numbers, figures, pictures, etc. The design layer 47 has, for example, a pattern. Examples of the patterns include wood grain patterns imitating tree rings or vessel grooves on the surface of a wooden board, stone grain patterns imitating the surface of rocks such as marble and granite, fabric patterns imitating cloth grain or cloth-like patterns, leather grain patterns imitating the surface of leather, pear-skin patterns, tile patterns, brickwork patterns, geometric patterns, and abstract patterns such as letters, figures, symbols, polka dots, and floral patterns. The pattern may be a single solid color (so-called solid image). The pattern may be a composite pattern including two or more of these. The design layer 47 may have two or more layers. For example, the design layer 47 may have a colored first layer and a second layer provided on the first layer to form the pattern.

[0103] The design layer 47 can be formed, for example, by printing or coating. Examples of methods for forming the design layer 47 by printing include gravure printing, offset printing, silk screen printing, printing by transfer from a transfer sheet, and inkjet printing. Examples of methods for forming the design layer 47 by coating include gravure coating, gravure reverse coating, gravure offset coating, spinner coating, roll coating, and reverse roll coating. When the design layer 47 is formed by printing or coating, the design layer 47 can be formed using ink. For example, an ink containing a binder resin and a colorant such as a pigment or dye can be used. The binder resin contained in the ink corresponds to the resin component contained in the design layer 47 described later. The colorant contained in the ink corresponds to the colorant contained in the design layer 47 described later. Each layer other than the design layer 47 contained in the covering sheet 30 described in this specification may also be formed by the method described above as the method for forming the design layer 47.

[0104] In one embodiment, the design layer 47 contains a resin component and a colorant. Examples of the resin component include vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl acetate-(meth)acrylic copolymer, chlorinated polyethylene, chlorinated polypropylene, urethane-(meth)acrylic copolymer, (meth)acrylic resin, (meth)acrylic polyol resin, polystyrene, polyurethane, polyester, polyamide, butyral resin, nitrocellulose, and cellulose acetate.

[0105] Examples of colorants include pigments and dyes. Specific examples include inorganic pigments such as carbon black, iron black, titanium white, antimony white, yellow lead, titanium yellow, red iron oxide, cadmium red, ultramarine blue, and cobalt blue; organic pigments or dyes such as quinacridone red, isoindolinone yellow, phthalocyanine blue, azomethine azo black, and nickel azo complex; metal pigments made of scaly flakes such as aluminum and brass; and pearlescent pigments made of scaly flakes such as titanium dioxide-coated mica and basic lead carbonate.

[0106] The content of colorant in the design layer 47 may be 5 parts by mass or more, 15 parts by mass or more, 30 parts by mass or more, 200 parts by mass or less, 150 parts by mass or less, or 100 parts by mass or less, relative to 100 parts by mass of the resin component contained in the design layer 47.

[0107] The design layer 47 may contain additives other than colorants. Examples of additives include ultraviolet absorbers, light stabilizers, antioxidants, fillers, defoamers, flame retardants, plasticizers, and lubricants. From the viewpoint of improving weather resistance, the design layer 47 may contain weather resistance agents such as ultraviolet absorbers, light stabilizers, and antioxidants.

[0108] The thickness of the design layer 47 is preferably 0.5 μm or more, more preferably 1 μm or more, and even more preferably 2 μm or more. The thickness of the design layer 47 is preferably 20 μm or less, more preferably 15 μm or less, and even more preferably 10 μm or less. This can improve the design of the decorative sheet, for example.

[0109] The design layer 47 may have a metal thin film. Examples of metals constituting the metal thin film include tin, indium, chromium, aluminum, nickel, iron, cobalt, copper, silver, gold, platinum, and zinc, as well as alloys containing at least one selected from these metals. Examples of alloys include brass, bronze, and stainless steel. Examples of methods for forming the metal thin film include vacuum deposition, sputtering, and ion plating. The thickness of the metal thin film is, for example, 0.1 μm or more and 1 μm or less.

[0110] By forming the steel structure 10 using the covering sheet 30 including the design layer 47 to cover the steel material 20, a design can be imparted to the surface of the steel structure 10. In particular, a design can be imparted to the surface of the steel structure 10 while repairing the steel structure 10. The effect of the design layer 47 will be explained in more detail by comparison with a comparative example. As a comparative example, consider a case where the steel structure 10 is repaired by laminating a coating film for suppressing corrosion on the deteriorated part 12 of the steel structure 10. In this case, the design can be imparted to the surface of the steel structure 10 by displaying the design on one of the laminated coating films. However, in this case, it becomes necessary to form a coating film that displays the design at the site where the steel structure 10 is installed. In this case, it takes a long time to repair the steel structure 10. Furthermore, it is difficult to form a coating film that displays a complex design at the site. In contrast, when repairing a steel structure 10 using a covering sheet 30 including a design layer 47, the steel structure 10 is repaired by covering the steel material 20 with a covering sheet 30 including a design layer 47 that has been prepared in advance. Therefore, since a design layer formed in advance is used, the time required for on-site repair work can be shortened. Furthermore, since a design layer formed in advance is used, a complex design can be easily imparted to the surface of the steel structure 10.

[0111] The covering sheet 30 of the present disclosure may include a concealing layer between the substrate 41 and the design layer 47. By providing the concealing layer, for example, it is possible to suppress the substrate 41 from adversely affecting the color tone or pattern imparted to the covering sheet 30 by the design layer 47.

[0112] The concealing layer may be an opaque layer. In one embodiment, the concealing layer contains a resin component and a colorant. The resin component and colorant contained in the concealing layer may be the same as those contained in the design layer 47. The concealing layer may contain the additives described above as the additives contained in the substrate 41 or the design layer 47. The thickness of the concealing layer is, for example, 0.5 μm or more and 20 μm or less.

[0113] <Barrier layer> The barrier layer 44 may be a vapor-deposited film formed on a resin film. The cover sheet 30 may include a barrier film including the barrier layer 44 and a resin film. In the example shown in FIG. 2A and FIG. 2B, the cover sheet 30 includes a barrier film 44X including the barrier layer 44 and a resin film 44a. The barrier layer 44 may be a vapor-deposited film formed on the substrate 41. When the barrier layer 44 and the substrate 41 form a barrier film, the bonding layer 491 bonding the barrier layer 44 and the substrate 41 shown in FIG. 2A and FIG. 2B can be omitted.

[0114] The covering sheet 30 including the barrier layer 44 can have excellent gas barrier properties. The covering sheet 30 including the barrier layer 44 can have excellent oxygen barrier properties and excellent water vapor barrier properties. The covering sheet 30 including the barrier layer 44 can suppress rusting of the steel material 20 and deterioration of the coating film on the steel material 20.

[0115] An example of the resin film 44a used in the barrier film 44X is the resin film constituting the above-mentioned base material 41. The thickness of the resin film 44a may be 5 μm or more, 10 μm or more, 100 μm or less, or 50 μm or less.

[0116] The barrier layer 44 may be a vapor-deposited film containing one or more metals, one or more inorganic oxides, or one or more metals and one or more inorganic oxides. Examples of metals contained in the vapor-deposited film include aluminum, chromium, tin, nickel, copper, silver, gold, and platinum. Examples of inorganic oxides include aluminum oxide, silicon oxide, magnesium oxide, calcium oxide, zirconium oxide, titanium oxide, boron oxide, hafnium oxide, barium oxide, and silicon carbide oxide (carbon-containing silicon oxide). As a specific example, the barrier layer 44 may include one or more of an aluminum vapor-deposited film, an aluminum oxide (alumina) vapor-deposited film, and a silicon oxide (silica) vapor-deposited film.

[0117] The thickness of the evaporated film may be 1 nm or more, 5 nm or more, or 10 nm or more. The thickness of the evaporated film may be 150 nm or less, 100 nm or less, or 80 nm or less.

[0118] The vapor deposition film constituting the barrier layer 44 may be formed by a physical vapor deposition method (PVD method) such as a vacuum deposition method, a sputtering method, or an ion plating method. The vapor deposition film constituting the barrier layer 44 may be formed by a chemical vapor deposition method (CVD method) such as a plasma chemical vapor deposition method, a thermal chemical vapor deposition method, or a photochemical vapor deposition method.

[0119] Examples of the vapor-deposited film include vapor-deposited polyester films such as vapor-deposited polyethylene terephthalate films, vapor-deposited polyamide films, and vapor-deposited polyolefins.

[0120] A layer containing an ultraviolet absorbing agent may be located between the barrier layer 44 and the first surface 31. The barrier layer 44 may deteriorate over time due to ultraviolet rays. Therefore, the layer containing an ultraviolet absorbing agent can suppress deterioration of the barrier layer 44 and maintain the gas barrier properties of the barrier layer 44. In the example shown in Figures 2A and 2B, one or more of the weather-resistant layer 42, the substrate 41, and the bonding layer 492 may contain an ultraviolet absorbing agent.

[0121] In the covering sheet 30 shown in FIG. 2A and FIG. 2B, as described above, the distance w6 between the barrier layer 44 and the second surface 32 is smaller than the distance w8 between the weathering layer 42 and the second surface 32. That is, the covering sheet 30 includes the barrier layer 44 and the weathering layer 42 in the order from the second surface 32 toward the first surface 31. The barrier layer 44 is located between the steel material 20 and the weathering layer 42 in the stacking direction. As a result, the barrier layer 44 is covered by the weathering layer 42 having weather resistance. As a result, the barrier layer 44 is protected by the weathering layer 42, and deterioration of the barrier layer 44 outdoors can be suppressed. As a result, the gas barrier property of the barrier layer 44 can be maintained. In particular, the barrier layer 44 is covered by the weathering layer 42 containing at least one of an ultraviolet absorbing agent and a light stabilizer as a weathering agent, and thus the barrier layer 44 can be protected from ultraviolet rays irradiated to the first surface 31 of the covering sheet 30. This makes it possible to suppress deterioration of the barrier layer 44 due to ultraviolet rays and maintain the gas barrier properties of the barrier layer 44. Since the weather-resistant layer 42 contains an ultraviolet absorber and a light stabilizer, it is possible to more stably suppress deterioration of the barrier layer 44 due to ultraviolet rays and maintain the gas barrier properties of the barrier layer 44.

[0122] As an example, the oxygen transmission rate (OTR, unit: cm 3 / (m 2 ·day)) is 6.57cm 3 / (m 2 The oxygen permeability of the covering sheet 30 is 3.0 cm 3 / (m 2 · day) or less is also acceptable, 2.5 cm 3 / (m 2 ·day) or less is also acceptable, 2.0cm 3 / (m 2 ·day) or less. The covering sheet 30 with adjusted oxygen permeability can suppress corrosion of the steel material 20 and deterioration of the coating film. The lower the oxygen permeability of the covering sheet 30, the more preferable it is. 3 / (m 2 ·day) or more is acceptable, 0.05 cm 3 / (m 2 ·day) or more is acceptable, 0.1cm 3 / (m2 10 days) or more is acceptable.

[0123] The oxygen permeability is a value measured in an environment of temperature 23°C and humidity 60% RH in accordance with JIS K7126-2:2006 "Appendix A (Regulations): Test method for oxygen gas permeability by electrolytic sensor method". In measuring the oxygen permeability, the cover sheet 30 is placed in a measuring device so that the first surface 31 is the oxygen supply side. The oxygen permeability measuring device may be "OX-TRAN 2 / 20" manufactured by MOCON, USA.

[0124] As an example, the water vapor transmission rate (WVTR, unit: g / (m 2 3.0g / (m 2 ·day) or less. The water vapor permeability of the covering sheet 30 is 2.5 g / (m 2 ·day) or less, and 2.0g / (m 2 ·day) or less. The covering sheet 30 with its water vapor permeability adjusted in this manner can suppress corrosion of the steel material 20 and deterioration of the coating film. The lower the water vapor permeability of the covering sheet 30, the more preferable it is. 2 ·day) or more, and 0.05g / (m 2 ·day) or more, and 0.1g / (m 2 10 days) or more is acceptable.

[0125] The water vapor permeability is a value measured in an environment at a temperature of 40°C and a humidity of 90% RH in accordance with JIS K7129-2:2019. In measuring the water vapor permeability, the covering sheet 30 is placed in a measuring device so that the first surface 31 is the hydrogen supply side. The measuring device for the water vapor permeability may be "PERMATRAN-w 3 / 33" manufactured by MOCON Corporation in the United States.

[0126] <Joining layer> The bonding layer 43, the bonding layer 491, and the bonding layer 492 contain a component having adhesive or cohesive properties. The bonding layer 43 bonds the covering sheet 30 to the steel material 20 or the coating film on the steel material 20. The bonding layer 491 bonds the barrier layer 44 to the substrate 41. In the example shown in Figures 2A and 2B, the bonding layer 491 bonds the resin film 44a included in the barrier film 44X to the substrate 41, thereby bonding the barrier layer 44 to the substrate 41. The bonding layer 492 bonds the design layer 47 to the transparent resin layer 48.

[0127] The bonding layer 43, the bonding layer 491, and the bonding layer 492 may be an adhesive layer or a sticky layer. Examples of the adhesive or sticky component include an acrylic resin, a vinyl chloride-vinyl acetate copolymer, a vinyl acetate resin, a polyolefin, a polyester, a polyurethane, a silicone resin, and a rubber-based resin.

[0128] The bonding layer 43, the bonding layer 491, and the bonding layer 492 may be a pressure-sensitive adhesive layer, that is, a pressure-sensitive adhesive layer. The pressure-sensitive adhesive layer is a layer formed of a pressure-sensitive adhesive (pressure-sensitive adhesive). The pressure-sensitive adhesive layer exhibits a tacky adhesive feeling at room temperature (e.g., 23°C). Examples of the pressure-sensitive adhesive include an acrylic pressure-sensitive adhesive, a urethane pressure-sensitive adhesive, a silicone pressure-sensitive adhesive, and a rubber pressure-sensitive adhesive. The application of an acrylic pressure-sensitive adhesive to the bonding layer 43 is preferable because of its excellent adhesion to the steel material 20, which may have unevenness, and to the coating film on the steel material 20. The acrylic pressure-sensitive adhesive also has excellent stability.

[0129] The bonding layer 43, the bonding layer 491, and the bonding layer 492 may contain additives. Examples of additives include pigments, dyes, colorants, antistatic agents, flame retardants, antifungal agents, crosslinking agents, tackifiers, plasticizers, leveling agents, flow control agents, defoamers, and dispersants. The bonding layer 43, the bonding layer 491, and the bonding layer 492 may contain weather resistance agents such as ultraviolet absorbers, antioxidants, and light stabilizers.

[0130] The storage modulus (G') at 40°C of the bonding layer 43, the bonding layer 491, and the bonding layer 492 may be 0.05 MPa or more and 1 MPa or less, 0.05 MPa or more and 0.8 MPa or less, 0.1 MPa or more and 1 MPa or less, or 0.1 MPa or more and 0.8 MPa or less. When the storage modulus (G') is equal to or more than the lower limit, excessive elongation of the adhesive layer when subjected to an impact can be suppressed. When the storage modulus (G') is equal to or less than the upper limit, breakage of the adhesive layer when subjected to an impact can be suppressed.

[0131] The storage modulus (G') is measured by the following method. Two test pieces 90 are prepared from the cover sheet 30 according to the method for preparing a test piece described in JIS K7244-1:1998, 6.2. Since the test piece 90 is prepared from the cover sheet 30, it includes a support 91 corresponding to the portion of the cover sheet 30 other than the bonding layer 43, and an adhesive layer 92 corresponding to the bonding layer to be measured for the storage modulus (G'). For example, when measuring the storage modulus (G') of the bonding layer 43, the test piece 90 includes the support 91 and the adhesive layer 92 corresponding to the bonding layer 43.

[0132] The method described herein can also measure the storage modulus (G') of the bonding layer 15 shown in Figure 1B. In this example, the test piece 90 includes a support 91 corresponding to the cover sheet 30 and an adhesive layer 92 corresponding to the bonding layer 15.

[0133] Next, the two test pieces 90 thus prepared are attached to a measuring device 70 as shown in FIG. 3. As shown in FIG. 3, the measuring device 70 includes a plate 71 and a jig 72. The jig 72 includes a pair of plate-like portions 73 sandwiching the plate 71. The plate 71 and the pair of plate-like portions 73 are spread in the vertical direction. The distance between the pair of plate-like portions 73 can be adjusted by rotating a nut 75 screwed to a bolt 74 that penetrates the pair of plate-like portions 73. The bolt 74 does not penetrate the plate 71 and the test piece 90 attached to the measuring device 70. The bolt 74 is located at a different position from the plate 71 and the test piece 90 in the direction perpendicular to the paper surface of FIG. 3. When attaching the two test pieces 90 to the measuring device 70, first, the two test pieces 90 are bonded to the plate 71 by the action of the adhesive layer 92 so that the plate 71 is sandwiched between the two test pieces 90. Next, the nut 75 is rotated to reduce the distance between the pair of plate-like portions 73, so that the plate 71 and the two test pieces 90 are sandwiched between the pair of plate-like portions 73, as shown in Fig. 3. In this way, the two test pieces 90 are fixed to the jig 72.

[0134] In addition, the thickness w1 of the test piece 90 is specified. The thickness w1 of the test piece 90 can be specified by the following method. Before the two test pieces 90 are fixed to the jig 72, the dimensions of the plate 71 and the jig 72 are specified. As the dimensions of the plate 71 and the jig 72, the thickness w2 of the plate 71 shown in FIG. 3 and the thicknesses w3 and w4 of the pair of plate-like portions 73 can be specified. The thicknesses w2, w3, and w4 can be specified by measuring with a vernier caliper. Furthermore, after the two test pieces 90 are fixed to the jig 72 as shown in FIG. 3, the dimensions of the jig 72 in a state in which the two test pieces 90 are sandwiched are specified. As the dimensions of the jig 72 in a state in which the two test pieces 90 are sandwiched, the distance w5 from one outer surface of the pair of plate-like portions 73 to the other outer surface of the pair of plate-like portions 73 shown in FIG. 3 can be specified. The distance w5 can be specified by measuring with a vernier caliper. Next, the thickness w1 of the test piece 90 is determined from the dimensions of the plate 71 and the jig 72, and the dimensions of the jig 72 holding the two test pieces 90. The thickness w1 of the test piece 90 can be calculated by subtracting the thicknesses w2, w3, and w4 from the distance w5 and dividing the result by 2. The determined thickness w1 of the test piece 90 is used to measure the storage modulus (G').

[0135] 3, after two test pieces 90 are fixed to a jig 72, the jig 72 is vibrated in the vertical direction. As a result, the vertical vibration is input to the adhesive layer 92 of the test pieces 90. By detecting the movement of the plate 71 when the vertical vibration is input to the adhesive layer 92 of the test pieces 90, the storage modulus (G') of the adhesive layer 92 can be measured.

[0136] The storage modulus (G') is measured under the following conditions. Atmosphere gas: Nitrogen Attachment mode: solid shear mode Temperature dependency measurement (heating is performed by a temperature program, and the elastic modulus is measured at each temperature at 10Hz) ·Basic frequency: 10Hz Measurement program: Start temperature = 30°C, Step temperature = 1°C, End temperature = 150°C, Heating rate: 3°C / min) Sine wave, stop excitation Manual static load: Adjust to 0g when fixing two test pieces 90 to the jig 72 Distortion: Value automatically set when sample length is entered 0.05 Auto adjustment mode

[0137] The storage modulus (G') can be measured using a solid viscoelasticity measuring device, such as Rheogel E4000 manufactured by UBM Corporation.

[0138] The thickness of the bonding layer 43, the bonding layer 491, and the bonding layer 492 may be 10 μm or more, 20 μm or more, 30 μm or more, 40 μm or more, or 50 μm or more. The thickness of the bonding layer 43, the bonding layer 491, and the bonding layer 492 may be 1000 μm or less, 500 μm or less, 300 μm or less, 250 μm or less, 200 μm or less, 180 μm or less, or 150 μm or less.

[0139] <Other layers that may be included in the covering sheet> The cover sheet 30 may include additional layers, without being limited to the examples shown in FIGS. 2A and 2B.

[0140] As an example, as shown by the two-dot chain line in FIG. 2A, the covering sheet 30 may further include a release film 46. Before the covering sheet 30 is bonded to the steel material 20, the release film 46 is bonded to the bonding layer 43. The release film 46 can protect the bonding layer 43 from foreign matter such as dust before the covering sheet 30 is used. When the covering sheet 30 is used, the release film 46 is removed from the covering sheet 30. By removing the release film 46, the bonding layer 43 is exposed, and the covering sheet 30 can be bonded to the steel material 20. Examples of the release film 46 include paper base materials and resin films, and those having a release agent applied to their surfaces. Examples of the release agent include silicone-based release agents, fluorine-based release agents, and long-chain alkyl-based release agents.

[0141] <<Other examples of layer configurations of covering sheets>> The layer structure of the covering sheet 30 is not limited to the example shown in Figures 2A and 2B. The distance w6 between the barrier layer 44 and the second surface 32 may be greater than the distance w7 between the design layer 47 and the second surface 32. That is, the design layer 47 and the barrier layer 44 may be laminated in this order from the second surface 32 toward the first surface 31. In the example shown in Figure 2C, the covering sheet 30 includes a base material 41, a design layer 47, a bonding layer 493, a barrier layer 44, a bonding layer 494, a transparent resin layer 48, and a weather-resistant layer 42 in this order from the second surface 32 toward the first surface 31 in the lamination direction.

[0142] 2C, the bonding layer 493 bonds the design layer 47 and the barrier layer 44. The bonding layer 494 bonds the barrier layer 44 and the transparent resin layer 48. In the example shown in Fig. 2C, the bonding layer 494 bonds the resin film 44a included in the barrier film 44X and the transparent resin layer 48, thereby bonding the barrier layer 44 and the transparent resin layer 48. The bonding layer 493 and the bonding layer 494 may be configured similarly to the bonding layer 43 of the cover sheet 30 described above.

[0143] The covering sheet 30 shown in Fig. 2C may also have weather resistance. In particular, the covering sheet 30 shown in Fig. 2C may also have resistance to ultraviolet light. From the viewpoint of reducing ultraviolet light that is irradiated onto the first surface 31 of the covering sheet 30 and reaches the barrier layer 44 by the design layer 47, it is preferable that the distance w6 is smaller than the distance w7 as shown in Figs. 2A and 2B.

[0144] <<<Other layers that may be included in steel structures>>> The steel structure 10 shown in Fig. 1B further includes a bonding layer 15 in addition to the steel material 20 and the covering sheet 30. The steel structure 10 shown in Fig. 1C further includes an anti-corrosive layer 18. Moreover, as shown by a two-dot chain line in Fig. 1C, the steel structure 10 may include a topcoat layer 19. The steel structure 10 is not limited to the examples shown in Figs. 1A to 1C, and may include further layers.

[0145] <<Joining layer>> 1B, the bonding layer 15 is used to bond the covering sheet 30 to the steel material 20. The bonding layer 15 may be configured similarly to the bonding layer 43 of the covering sheet 30 described above.

[0146] <<Anti-rust layer>> The anticorrosive layer 18 is located between the steel material 20 and the covering sheet 30. The anticorrosive layer 18 suppresses corrosion of the steel material 20. The anticorrosive layer 18 suppresses the spread of corrosion in the steel material 20. As shown in Figures 1A and 1B, the anticorrosive layer 18 can be omitted from the steel material 20.

[0147] The anticorrosive layer 18 may be produced by forming a coating film by applying an anticorrosive paint containing an anticorrosive agent to the surface of the steel material 20, and then solidifying or curing the coating film. Examples of the coating method include brush coating, roller coating, and spray coating (e.g., air spray, airless spray). The anticorrosive layer 18 formed as a coating film can improve adhesion to the uneven surface of the steel material 20.

[0148] The thickness of the anticorrosive layer 18 may be 10 μm or more, 30 μm or more, 50 μm or more, 100 μm or more, or 150 μm or more. The thickness of the anticorrosive layer 18 may be 1000 μm or less, 800 μm or less, 600 μm or less, or 500 μm or less. By setting a lower limit value for the thickness of the anticorrosive layer 18, it is possible to impart sufficient anticorrosive function to the anticorrosive layer 18. By setting an upper limit value for the thickness of the anticorrosive layer 18, it is possible to improve the workability and cost when producing the anticorrosive layer 18.

[0149] Examples of the rust inhibitor contained in the rust-preventive layer 18 include inorganic rust inhibitors and organic rust inhibitors. The inorganic rust inhibitor may be an inorganic acid or a salt of an inorganic acid. Examples of the inorganic rust inhibitor include red lead, lead suboxide, basic lead chromate, lead dianamidate, calcium plumbate, basic lead sulfate, zinc chromate, zinc powder, red iron oxide, nitrite, sulfite, silicate, metasilicate, phosphate, polyphosphate, hypophosphite, phosphite, molybdate, phosphomolybdate, borate, metaborate, tungstate, carbonate, and chromate. Examples of the inorganic rust inhibitor include a phosphate compound, a vanadium compound, a niobium compound, a zirconium compound, and zinc oxide. Examples of the inorganic rust inhibitor include an ammonium salt, a calcium salt, a magnesium salt, an aluminum salt, a zinc salt, a manganese salt, and a barium salt.

[0150] Examples of organic rust inhibitors include organic amine compounds, organic amine salts, tannic acid, carboxylic acids, and esters or salts of these acids. Examples of organic rust inhibitors include sulfonates, organic phosphates, benzotriazole compounds, benzothiazole compounds, mercaptan compounds, guanidino group-containing compounds, pyruguanidino group-containing compounds, thiocarbonyl group-containing compounds, alkylphenol compounds, diisopropylammonium nitrite, and dicyclohexylammonium nitrite.

[0151] Examples of the anti-rust paint include epoxy resin paint, urethane resin paint, acrylic resin paint, silicon acrylic resin paint, styrene resin paint, fluororesin paint, and zinc rich paint containing an organic binder and zinc powder. The anti-rust paint may include a binder and a rust inhibitor. Examples of the binder of the anti-rust paint include organic binders such as epoxy resin, urethane resin, acrylic resin, silicon acrylic resin, styrene resin, and fluororesin. Examples of the binder of the anti-rust paint include inorganic binders such as alkyl silicate.

[0152] From the viewpoint of the rust prevention mechanism, rust inhibitors, rust prevention paints, and rust prevention layers using these can be classified into a rust conversion type, a salt / iron ion neutralizing type, and a type that prevents rust by stabilizing iron ions with a two-component curing ion trapping agent. The rust inhibitor and rust prevention paint used in the rust inhibitor layer 18 may be a rust conversion type, a salt / iron ion neutralizing type, or a type that prevents rust by stabilizing iron ions with a two-component curing ion trapping agent.

[0153] The steel structure 10 includes the rust-preventive layer 18 formed using the rust inhibitor and the rust-preventive paint, so that the steel material 20 is less likely to develop red rust. On the other hand, the rust-conversion type rust inhibitor and the rust-preventive paint generate black rust when exerting the rust-preventive effect on the steel material. The strength of the steel material 20 can be secured more when the steel material 20 has black rust caused by the rust-conversion type rust inhibitor and the rust-preventive paint than when the steel material 20 has red rust. Therefore, the strength of the steel material 20 can be secured even by forming the rust-preventive layer 18 using the rust-conversion type rust inhibitor and the rust-preventive paint. However, the strength of the steel material 20 can be secured more when the steel material 20 has neither black rust nor red rust than when the steel material 20 has black rust. The rust inhibitor and the rust-preventive paint of the salt / iron ion neutralizing type and the type of iron ion stabilization by the two-liquid curing ion trapping agent do not generate black rust when exerting the rust-preventive effect on the steel material. Furthermore, the rust-preventive layer 18 formed by a rust inhibitor and anti-rust paint of the type that renders salt and iron ions harmless or the type that stabilizes iron ions using a two-component curing ion trap agent also makes it difficult for red rust to occur on the steel material 20. For this reason, from the viewpoint of ensuring greater strength of the steel material 20, it is preferable to use a rust inhibitor and anti-rust paint of the type that renders salt and iron ions harmless or the type that stabilizes iron ions using a two-component curing ion trap agent for forming the rust-preventive layer 18, rather than using a rust inhibitor and anti-rust paint of the rust conversion type.

[0154] The anti-rust paint may be a one-component curing type anti-rust paint, or may be a two-component curing type anti-rust paint containing a main agent and a curing agent. The two-component curing type anti-rust paint may be used by storing the main agent containing a binder and, if desired, a rust inhibitor in a separate container, and mixing the two immediately before use. The two-component curing type anti-rust paint is excellent in that it has high adhesion to the steel material 20, high coating strength, and can make the anti-rust layer 18 dense. The two-component curing type anti-rust paint is also excellent in adhesion to the covering sheet 30. The two-component curing type anti-rust paint may be a two-component curing type epoxy resin paint, or may be a two-component curing type urethane resin paint.

[0155] The two-component curing epoxy resin paint may contain an epoxy resin as a binder and an epoxy resin curing agent as a curing agent. Examples of the curing agent include amine-based curing agents, phenol-based curing agents, acid anhydride-based curing agents, and mercaptan-based curing agents. The urethane resin paint may be a two-component curing type consisting of a polyol-based compound and an isocyanate-based compound, or a one-component curing type that is cured by moisture in the air.

[0156] The anti-rust paint may contain a moisture-curing resin. The moisture-curing resin has an isocyanate group as a reactive group. The isocyanate group of the moisture-curing resin reacts with water and hardens according to the reaction shown in the following formula (I). That is, first, the isocyanate group of the moisture-curing resin reacts with water to generate carbamic acid. Then, the carbamic acid is decomposed to generate an amine. Then, the amine reacts with the isocyanate group of the moisture-curing resin to cause a crosslinking reaction in which a urea bond is generated. This crosslinking reaction hardens the moisture-curing resin. When the anti-rust paint contains a moisture-curing resin, a rust-preventing effect is obtained by removing water, which can be a corrosion factor. [ka]

[0157] As an example, the moisture-curing resin contained in the anti-rust paint is a urethane resin. In this case, the anti-rust paint may be a two-component curing urethane resin paint that neutralizes salt and iron ions.

[0158] When the rust-preventive paint contains a moisture-curing resin, as shown in the above formula (I), carbon dioxide gas may be generated by the moisture-curing resin reacting with water. As shown in FIG. 4D, when the covering sheet and the rust-preventive layer cover the steel material, from the viewpoint of suppressing the generated carbon dioxide gas from passing through the covering sheet and remaining in the covering sheet as bubbles, it is preferable that the covering sheet is not provided with oxygen barrier properties. By not providing oxygen barrier properties to the covering sheet, carbon dioxide gas can easily pass through the covering sheet, and carbon dioxide gas can be suppressed from remaining in the covering sheet as bubbles. From the above, when a rust-preventive paint containing a moisture-curing resin is used, from the viewpoint of suppressing the occurrence of poor appearance due to carbon dioxide gas remaining in the covering sheet as bubbles, it is preferable that the covering sheet is not provided with oxygen barrier properties.

[0159] On the other hand, in particular, when an anti-rust paint that does not contain a moisture-curing resin is used, it is preferable that the covering sheet is provided with oxygen barrier properties in order to prevent oxygen, which may be a corrosion factor, from reaching the anti-rust layer and the steel material. In particular, when an anti-rust paint that does not contain a moisture-curing resin is used, even if the covering sheet is provided with oxygen barrier properties, air bubbles may not be generated in the covering sheet. Therefore, when an anti-rust paint that does not contain a moisture-curing resin is used, by providing the covering sheet with oxygen barrier properties, it is possible to prevent oxygen from reaching the anti-rust layer and the steel material, while preventing poor appearance due to carbon dioxide gas remaining in the covering sheet as air bubbles.

[0160] The rust-preventive paint may be colored or may not be colored. When the rust-preventive paint contains a moisture-curing resin, the rust-preventive paint containing the moisture-curing resin may be colored or may not be colored. The rust-preventive paint that does not contain a moisture-curing resin and is not colored may be, for example, a type of rust-preventive paint that prevents rust by stabilizing iron ions with the above-mentioned two-component curing ion trapping agent.

[0161] As an example, the oxygen transmission rate (OTR) of a covering sheet with oxygen barrier properties is 6.57cc / (m 2 ·day·atm).

[0162] Regardless of whether the anti-rust paint contains a moisture-curing resin, the coating sheet may be provided with water vapor barrier properties. This makes it difficult for water, which can be a corrosive factor, to reach the anti-rust layer and the steel material. As an example, the water vapor transmission rate (WVTR) of a coating sheet provided with water vapor barrier properties is 3.0 g / (m 2 ·day) or less.

[0163] The anti-rust paint may contain additives. Examples of additives include rosins, plasticizers, extender pigments, coloring pigments, solvents, hardening accelerators, coupling agents, corrosive ion fixing agents, anti-sagging agents, and anti-settling agents. Examples of coupling agents include silane-based coupling agents, titanium-based coupling agents, aluminum-based coupling agents, and zirconium-based coupling agents. Examples of corrosive ion fixing agents include hydrotalcite and hydrocalumite.

[0164] The 85-degree specular gloss of the surface of the anticorrosive layer 18 provided on the steel material 20 may be 3 or more. The 85-degree specular gloss of the surface of the anticorrosive layer 18 may be 5 or more, 10 or more, 15 or more, 20 or more, or 23 or more. By setting the lower limit of the 85-degree specular gloss of the surface of the anticorrosive layer 18 in this manner, the anticorrosive layer 18 becomes a dense film. The anticorrosive layer 18 as a dense film exhibits high adhesion with the covering sheet 30. The upper limit of the 85-degree specular gloss of the surface of the anticorrosive layer 18 is not particularly limited. The 85-degree specular gloss of the surface of the anticorrosive layer 18 may be 60 or less, 50 or less, or 40 or less.

[0165] The specular gloss is measured in accordance with JIS Z8741:1997, except that the angle of incidence is set to 85°. The measurement environment for measuring specular gloss is a temperature of 23°C ± 2°C and a relative humidity of 50% ± 5%. The measurement sample to be measured is placed in the measurement environment for 16 hours before starting the measurement. Before measuring specular gloss, the light source of the measuring device is turned on for 15 minutes to stabilize the light source output.

[0166] The specular gloss is the arithmetic mean of five measurements taken at five measurement positions on the sample to be evaluated, the five measurement positions being at least 10 mm apart from each other.

[0167] A lower limit may be set for the retention rate of 85 degree specular gloss for the anticorrosive layer 18 provided on the steel material 20. By setting a lower limit for the retention rate of 85 degree specular gloss on the surface of the anticorrosive layer 18, it is possible to ensure the adhesion of the anticorrosive layer 18 to the steel material 20. The retention rate of 85 degree specular gloss on the surface of the anticorrosive layer 18 may be 60% or more, 70% or more, 80% or more, 90% or more, or 95% or more.

[0168] The 85-degree specular gloss retention rate is the retention rate of the 85-degree specular gloss on the surface of the anti-rust layer 18 before and after the 90-degree tape peel test is performed. The 85-degree specular gloss on the surface of the anti-rust layer 18 before the 90-degree tape peel test is performed on the anti-rust layer 18 is defined as "Gsb". The 85-degree specular gloss on the surface of the anti-rust layer 18 after the 90-degree tape peel test is performed on the anti-rust layer 18 is defined as "Gsa". The 85-degree specular gloss retention rate is expressed as Gsa x 100 / Gsb, and is expressed in %,.

[0169] The 90-degree tape peeling test is carried out as follows. 25 cm of a 24 mm wide cellophane adhesive tape conforming to JIS Z1522:2009 is unwound from a roll at a temperature of 23°C ± 2°C and a relative humidity of 50% ± 5%, and 10 cm of the adhesive surface is attached to the surface of the rust-proofing layer of the steel structure with a 2 kg pressure roller in two passes, and then the adhesive surface is again attached by finger pressure so that no air is interposed. Next, the cellophane adhesive tape is manually peeled once at a speed of 5 cm / s in a 90-degree direction against the surface of the rust-proofing layer. Cellotape (registered trademark) (manufactured by Nichiban, model No. 405-1P, 24 mm wide) is used as the cellophane adhesive tape. If the product cannot be used, a 24 mm wide cellophane adhesive tape conforming to JIS Z1522:2009 with the same adhesive strength as the product is used.

[0170] <<Topcoat layer>> The topcoat layer 19 is formed on the covering sheet 30. In this example, the covering sheet 30 is located between the topcoat layer 19 and the steel material 20 in the lamination direction. The topcoat layer 19 may be provided for the purpose of improving the weather resistance of the steel structure 10. The topcoat layer 19 may provide the steel structure 10 with excellent rust prevention properties for a long period of time. The topcoat layer 19 can be omitted from the steel structure 10.

[0171] The topcoat layer 19 may be produced by applying a topcoat paint to the first surface 31 of the cover sheet 30 to form a coating film, and then solidifying or curing the coating film. Examples of the coating method include brush coating, roller coating, and spray coating (e.g., air spray, airless spray). The topcoat paint may be a one-component paint or a two-component paint. The topcoat layer 19 and the topcoat paint may contain a resin and an additive.

[0172] Examples of the resin contained in the topcoat layer 19 and the topcoat paint include fluororesin, urethane resin, acrylic resin, butadiene resin, silicone resin, vinyl ester resin, and epoxy resin. Examples of the fluororesin include polyvinyl fluoride, polytetrafluoroethylene, perfluoroalkoxyalkane, and ethylene-tetrafluoroethylene copolymer. Examples of the additives contained in the topcoat layer 19 and the topcoat paint include pigments, dyes, dispersants, defoamers, thickeners, leveling agents, anti-settling agents, anti-sagging agents, anti-algae agents, anti-mildew agents, preservatives, ultraviolet absorbers, antioxidants, and light stabilizers.

[0173] The topcoat paint may contain an organic solvent and / or water for the purpose of adjusting the viscosity, etc. Examples of organic solvents include aromatic hydrocarbons, aliphatic hydrocarbons, ketones, acetates, ethers, alcohol-based solvents, and mineral spirits.

[0174] The thickness of the topcoat layer 19 may be 5 μm or more, 10 μm or more, or 15 μm or more. The thickness of the topcoat layer 19 may be 200 μm or less, 150 μm or less, or 100 μm or less.

[0175] Next, a method for repairing the steel structure 10 using the covering sheet 30 will be described.

[0176] The covering sheet 30 described above can facilitate preventive maintenance work, as will be described below. In preventive maintenance, repairs are carried out on deteriorated parts of steel materials before they develop into serious defects.

[0177] As an example, the steel structure 10 to be repaired may be a steel structure 10 including a covering sheet 30, as shown in Figures 1A to 1C. As another example shown in Figure 5, the steel structure 10 to be repaired may be a steel structure 100 including a steel material 20 and a number of coating films 50 formed on the steel material 20.

[0178] 5 shows a conventional steel structure 100 including multiple coatings 50. The coatings 50 included in the steel structure 100 include, in order from the steel material 20, an anti-corrosive layer 51, a first undercoat layer 52, a second undercoat layer 53, an intermediate coat layer 54, and a top coat layer 55.

[0179] The anticorrosive layer 51 has an anticorrosive function. The anticorrosive layer 51 is a layer that suppresses the generation and spread of rust. The anticorrosive layer 51 may be configured in the same manner as the anticorrosive layer 18 described above.

[0180] The first undercoat layer 52 and the second undercoat layer 53 have gas barrier properties. The first undercoat layer 52 and the second undercoat layer 53 suppress corrosion of the steel material 20. The barrier properties of a barrier layer that is a coating film are weaker than those of a barrier layer that is a vapor deposition film. The illustrated steel structure 100 includes two undercoat layers 52, 53 to ensure sufficient barrier properties. The undercoat layers 52, 53 may include an epoxy resin. The undercoat layers 52, 53 may include a cured product of a curable resin.

[0181] The intermediate coating layer 54 has high adhesion. The intermediate coating layer 54 improves the adhesion of the top coating layer 55. An example of an intermediate coating layer having high adhesion is a layer containing a fluorine-based resin. The intermediate coating layer 54 may contain weathering agents such as an ultraviolet absorber, an antioxidant, and a light stabilizer.

[0182] The overcoat layer 55 has weather resistance. The overcoat layer 55 contains weather-resistant agents such as an ultraviolet absorber, an antioxidant, and a light stabilizer. An example of the overcoat layer 55 is a layer containing a fluorine-based resin and a weather-resistant agent. The overcoat layer 55 may be configured in the same manner as the overcoat layer 19 described above.

[0183] Each of the multiple coating films 50 is applied one layer per day, taking into consideration the time required for drying, hardening, curing, etc. For example, the steel structure 100 shown in Fig. 5 requires five days for construction.

[0184] A method for repairing the steel structure 100 shown in Fig. 5 will be described with reference to Fig. 4A to Fig. 4D. A covering sheet 30 is used for the repair. The repaired steel structure 10 includes the covering sheet 30. The repair is not limited to the example shown in Fig. 4A to Fig. 4D, and the steel structure 10 including the covering sheet 30 may be repaired using the covering sheet 30.

[0185] The repair method includes a step of performing surface preparation for the deteriorated portion 12 of the steel structure 100, and a step of covering the steel material 20 of the steel structure 100 that has been surface-prepared with a covering sheet 30. The repair method shown in Figs. 4A to 4D includes a first step, a second step, a third step, and a fourth step. In the first step, the covering sheet 30 is prepared. In the second step shown in Fig. 4B, surface preparation is performed for the deteriorated portion 12 of the steel structure 100. In the third step shown in Fig. 4C, the rust-preventive layer 18 is formed. In the fourth step shown in Fig. 4D, the covering sheet 30 is joined to the steel material 20. Each step will be described in order below.

[0186] Fig. 4A is a cross-sectional view that shows a schematic diagram of a deteriorated portion 12 of a steel structure. In Fig. 4A, a pre-repair coating film (old coating film) 50 is provided on a steel material 20. Rust 60 has developed on the steel material 20. To repair such deteriorated portion 12, the above-mentioned covering sheet 30 is prepared as a first step.

[0187] As shown in Fig. 4B, in the second step, surface preparation (base preparation) is performed on the deteriorated portion 12 of the steel structure 100. Scraping is an example of a method for adjusting the base of the steel structure 100. In scraping, old paint films, rust, dust, dirt, etc. are generally removed by blasting or using power tools or hand tools. By removing these, a surface preparation surface 22 is exposed. In the second step, the surface preparation surface 22 constitutes the surface of the steel structure 100.

[0188] Scraping is classified into three grades: Class 1, Class 2, Class 3, and Class 4. The lower the grade number, the higher the level of surface preparation.

[0189] "Type 1 scraping" refers to surface preparation that exposes the steel surface by removing all rust and old paint film 50. In "Type 1 scraping", surface preparation is mainly performed by blasting.

[0190] "Type 2 scraping" refers to surface preparation in which rust and old paint film 50 are removed to expose the surface of steel material 20. In "Type 2 scraping", surface preparation is performed mainly with power tools and / or hand tools.

[0191] "Type 3 scraping" is a surface preparation method that leaves active film 50P of old paint film 50, i.e., the paint film in a healthy state, but removes other defective parts (rust and dead films of the old paint film (paint film with cracks and blisters)). In "Type 3 scraping", surface preparation is mainly performed with power tools and / or hand tools.

[0192] The advantage of type 3 scraping is that fewer work areas are required and work costs are lower than with type 1 and type 2 scraping. Since the active film 50P of the old coating film 50 remains, the surface preparation surface after type 3 scraping may have large irregularities. Rust may remain on the surface preparation surface after type 3 scraping. The height of the irregularities on the surface of the steel structure 10 after type 3 scraping may be 10 μm or more and 1000 μm or less, 30 μm or more and 500 μm or less, or 50 μm or more and 300 μm or less.

[0193] Fig. 4B shows a steel structure 100 that has been subjected to surface preparation using a type 3 scraper. In Fig. 4B, the old paint film 50 has been removed except for the active film 50P. In Fig. 4B, rust 60 has also been removed.

[0194] "Type 4 scraping" is a surface preparation that removes powdered matter (including loose rust) and dirt that has adhered to the surface. In "Type 4 scraping", the surface preparation is mainly done with hand tools and / or brushes.

[0195] Examples of power tools include a disk sander and a wire wheel, and examples of hand tools include a wire brush, a scraper, a scraping bar, and sandpaper.

[0196] In the third step, as shown in Fig. 4C, a rust-proofing treatment is performed on the surface preparation surface 22 of the steel structure 100. In the third step, a rust-proofing layer 18 is formed on the steel material 20 and the active film 50P. The material and the method of forming the rust-proofing layer 18 are as described above.

[0197] The rust-preventive layer 18 contains a rust inhibitor. The rust inhibitor can suppress rust generation. The rust inhibitor may be contained in the bonding layer 15 or the covering sheet 30. When the rust inhibitor is contained in the covering sheet 30, for example, the rust inhibitor may be contained in the bonding layer 43. By providing the rust-preventive layer 18 containing the rust inhibitor separately from the covering sheet 30, the effect of the rust inhibitor can be obtained more clearly. The rust-preventive layer 18 formed as a coating film can fill in the unevenness of the base preparation surface having unevenness to a certain extent. This can improve the adhesion of the covering sheet 30.

[0198] In the fourth step, the steel material 20 of the steel structure 100, which has been subjected to surface preparation, is covered with the covering sheet 30. In the fourth step, the covering sheet 30 is placed on the steel structure 100 under repair. As a result, the steel material 20 is covered with the covering sheet 30. In the example shown in FIG. 4D, the covering sheet 30 is placed on the anticorrosive layer 18. The covering sheet 30 including the bonding layer 43 is bonded to the anticorrosive layer 18 using the bonding layer 43. In the example shown in FIG. 4D, the bonding layer 15 is formed on the anticorrosive layer 18, and the covering sheet 30 is bonded to the anticorrosive layer 18 using this bonding layer 15. In the fourth step, the steel structure 10 including the covering sheet 30 is obtained.

[0199] The covering sheet 30 may be attached to the steel structure 10 by the bonding layers 15, 43 while being pressed at room temperature. For example, the covering sheet 30 may be pressed toward the steel material 20 from above the covering sheet 30 using a roller or the like. This allows the covering sheet 30 to be tightly attached to the steel material 20 or the coating film on the steel material 20 (e.g., the anticorrosive layer 18).

[0200] When the covering sheet 30 includes the release film 46, the release film 46 is peeled off from the covering sheet 30 before the covering sheet 30 is placed on the steel material 20. By peeling off the release film 46, the bonding layer 43 is exposed.

[0201] The covering sheet 30 may cover the side end portion of the anticorrosive layer 18. The covering sheet 30 may be folded to cover the side end surface of the steel structure 10.

[0202] As described above, the steel structure is repaired using the covering sheet 30, and the steel structure 10 including the covering sheet 30 is obtained. By using the covering sheet 30 for repair, the repair of the steel structure can be performed in a short time. For example, compared to re-forming a large number of coating films 50 shown in FIG. 5 at the repair location, the use of the covering sheet 30 can significantly shorten the construction period. In addition, the repair using the covering sheet 30 can reduce costs and facilitate construction. Furthermore, by using the covering sheet 30 produced in a factory with a well-maintained environment, the occurrence of defects such as pinholes can be suppressed compared to forming a large number of coating films on the steel material 20 outdoors. As described above, the use of the covering sheet 30 can facilitate preventive maintenance. The steel structure 10 including the covering sheet 30 obtained by repair can facilitate inspection for the purpose of finding abnormalities.

[0203] The method for repairing a steel structure using the covering sheet 30 is not limited to the method described above with reference to FIGS. 4A to 4D.

[0204] In the illustrated example, type 3 scraping is performed as the surface preparation in the second step. However, the repair method using the covering sheet 30 is not limited to this example. The repair method using the covering sheet 30 can be applied to steel structures in which type 1 scraping, type 2 scraping, and type 4 scraping other than type 3 scraping are performed as the surface preparation.

[0205] Before the fourth step is performed, a step of forming a flattening layer may be performed. The flattening layer may be formed on the base preparation surface 22 or on the anticorrosive layer 18. By providing the flattening layer, the surface to which the covering sheet 30 is bonded is flattened. This can improve the adhesion of the covering sheet 30 to the steel structure 10.

[0206] Examples of materials constituting the planarization layer include fluororesin, acrylic resin, silicone resin, urethane resin, urea resin, and epoxy resin. The planarization layer may be produced by applying a coating material to form a coating film and solidifying or curing the coating film. The coating material may be a one-component curing coating material or a two-component curing coating material. The planarization layer may contain additives such as ultraviolet absorbers, antioxidants, and light stabilizers.

[0207] The third step may be omitted from the above-described repair method. When the third step is omitted, the cover sheet 30 is bonded to the substrate preparation surface 22. The above-described repair method may also include a step of forming the topcoat layer 19.

[0208] As already mentioned, the repair of the steel structure 10 including the covering sheet 30 may be performed using the covering sheet 30, without being limited to the examples shown in FIGS.

[0209] (Modification) Next, a modified example of this embodiment will be described with reference to Figures 6 to 11. In Figures 6 to 11, the same parts as those in the embodiment shown in Figures 1A to 5 are given the same reference numerals and detailed description will be omitted.

[0210] In the above embodiment, the cover sheet 30 includes the substrate 41 as a component separate from the design layer 47. However, the form of the cover sheet 30 is not limited to this. Fig. 6 shows a cross section of the cover sheet 30 of this modification taken along the normal direction.

[0211] 6 is a colored colored substrate 471. The colored substrate 471 can be considered as a component that provides the design layer 47, which imparts a desired design to the covering sheet 30, with the function of the substrate 41. In this modification, the colored substrate 471 is colored in a single color.

[0212] As the material for the colored substrate 471, a material capable of coloring the colored substrate 471 to a desired color can be selected from the materials described above as the materials for the substrate 41. The colored substrate 471 may contain the resin material described above as the materials for the substrate 41 and the colorant described above as the materials for the substrate 41.

[0213] The covering sheet 30 shown in Fig. 6 further includes a bonding layer 43, and a release film 46 covering the bonding layer 43. The covering sheet 30 shown in Fig. 6 includes, in this order from the second surface 32 to the first surface 31 in the stacking direction, the release film 46, the bonding layer 43, a barrier film 44X, a bonding layer 491, a design layer 47 which is a colored base material 471, and a weather-resistant layer 42.

[0214] Fig. 7 is a plan view showing an example of a steel structure 10 provided with the covering sheet 30 of this modified example, observed from the normal direction of the covering sheet 30. Fig. 8 is a cross-sectional view of the steel structure 10 taken along line VIII-VIII in Fig. 7. In Figs. 7 and 8, the components of the covering sheet 30 shown in Fig. 6 are omitted, and only the outer shape of the covering sheet 30 is shown.

[0215] The steel structure 10 shown in Figures 7 and 8 is a steel structure 10 after repair using the covering sheet 30 of this modified example. The steel structure 10 shown in Figures 7 and 8 has a repaired portion 10a and a non-repaired portion 10b. The repaired portion 10a corresponds to an area where surface preparation was performed when the steel structure 100 was repaired using the covering sheet 30. The non-repaired portion 10b corresponds to an area where surface preparation was not performed when the steel structure 100 was repaired using the covering sheet 30. As will be described later, the process of performing surface preparation on the deteriorated portion 12 of the steel structure 100 in the repair method of the steel structure 10 of this modified example includes a process of performing one, two, or three types of scraping treatment on the deteriorated portion 12. In a steel structure 10 after repair by such a repair method, the repaired portion 10a is an area where the coating film 50 formed on the steel material 20 in the steel structure 100 before repair has been removed, and an area surrounded by the area where the coating film 50 has been removed. An area where a part of the coating film 50 remains on the steel material 20, such as an active film 50P in FIG. 9B described later, is also included in the repaired portion 10a as long as it is surrounded by an area where the coating film 50 has been removed. The non-repaired portion 10b is an area other than the repaired portion 10a in the steel structure 10 after repair using the covering sheet 30. In the non-repaired portion 10b, the coating film 50 formed on the steel material 20 in the steel structure 100 before repair remains unremoved.

[0216] The non-repaired portion 10b is colored. As an example, the coating film 50 of the non-repaired portion 10b is colored, thereby coloring the non-repaired portion 10b. In this modification, the non-repaired portion 10b is colored with a single color.

[0217] In the steel structure 10 of this modified example, the covering sheet 30 is located at least in a part of the repaired portion 10a. In the steel structure 10 shown in Figures 7 and 8, the covering sheet 30 is located in the entire repaired portion 10a. In the steel structure 10 shown in Figures 7 and 8, the covering sheet 30 is located in the entire repaired portion 10a and in a part of the non-repaired portion 10b. The covering sheet 30 is not located in any other part of the non-repaired portion 10b.

[0218] In the steel structure 10 of this modified example, the colored base material 471 is colored the same color as the non-repaired portion 10b. That is, in the steel structure 10 of this modified example, the design layer 47 of the covering sheet 30 is the colored base material 471 colored the same color as the non-repaired portion 10b. "The same color" means that the two colors of the object are perceived as the same color by a person with normal visual ability observing an object such as the steel structure 10.

[0219] The steel structure 10 of this modification further includes a first colored coating film 81 of the same color as the non-repaired portion 10b, which is formed so as to cover the portion of the steel material 20 located at the repaired portion 10a and the covering sheet 30. In the steel structure 10 shown in FIG. 8, the first colored coating film 81 is formed on the first surface 31 of the covering sheet 30. In the steel structure 10 shown in FIG. 8, the first colored coating film 81 covers the portion of the steel material 20 located at the repaired portion 10a and the entire covering sheet 30. In the steel structure 10 shown in FIG. 8, the first colored coating film 81 covers a part of the portion of the steel material 20 located at the non-repaired portion 10b. In this modification, the first colored coating film 81 is given a single color.

[0220] The steel structure 10 of this modification further includes an anticorrosive layer 18 formed on the surface of the portion of the steel material 20 located at the repaired portion 10a. In the steel structure 10 shown in FIG. 8, the anticorrosive layer 18 covers the entire portion of the steel material 20 located at the repaired portion 10a. In the steel structure 10 shown in FIG. 8, the anticorrosive layer 18 covers a portion of the portion of the steel material 20 located at the non-repaired portion 10b. In the steel structure 10 shown in FIG. 8, the covering sheet 30 covers at least a portion of the anticorrosive layer 18, particularly the entire anticorrosive layer 18. In the steel structure 10 shown in FIG. 8, the first colored coating film 81 covers at least a portion of the anticorrosive layer 18, particularly the entire anticorrosive layer 18. In the steel structure 10 shown in FIG. 8, the anticorrosive layer 18 is located between the steel material 20 and the covering sheet 30.

[0221] The steel structure 10 of this modification further includes a second colored coating film 82 formed on the surface of the anticorrosive layer 18. In the steel structure 10 shown in FIG. 8, the second colored coating film 82 covers the entire portion of the steel material 20 located in the repaired portion 10a. In the steel structure 10 shown in FIG. 8, the second colored coating film 82 covers the entire anticorrosive layer 18. In the steel structure 10 shown in FIG. 8, the second colored coating film 82 covers a part of the portion of the steel material 20 located in the non-repaired portion 10b. In the steel structure 10 shown in FIG. 8, the covering sheet 30 covers at least a part of the second colored coating film 82, particularly the entire second colored coating film 82. In the steel structure 10 shown in FIG. 8, the first colored coating film 81 covers at least a part of the second colored coating film 82, particularly the entire second colored coating film 82. In the steel structure 10 shown in Fig. 8, the second colored coating film 82 is located between the anticorrosive layer 18 and the covering sheet 30. In this modification, the second colored coating film 82 is given a single color.

[0222] 8 includes, in a repaired portion 10a, a steel material 20, an anticorrosive layer 18, a second colored coating film 82, a covering sheet 30, and a first colored coating film 81, in this order in the stacking direction. In the steel structure 10 shown in FIG. 8, a bonding layer 43 of the covering sheet 30 bonds the covering sheet 30 to the second colored coating film 82.

[0223] 9A to 9F, a method for repairing a steel structure 100 having a deteriorated portion 12 to form a steel structure 10 having a repaired portion 10a and a non-repaired portion 10b as shown in FIG. 7 and FIG. 8 will be described. The method for repairing a steel structure of this modification includes a step of performing a surface preparation for the deteriorated portion 12 of the steel structure 100, and a step of covering the steel material 20 of the steel structure 100 whose surface has been prepared with a covering sheet 30. The method for repairing a steel structure of this modification further includes a step of forming a first colored coating film 81 having the same color as the undeteriorated portion 13 described below so as to cover the surface-prepared portion of the steel structure 100 and the covering sheet 30. The method for repairing a steel structure of this modification further includes a step of forming an anticorrosive layer 18 on the surface of the surface-prepared portion of the steel structure 100. The method for repairing a steel structure of this modification further includes a step of forming a second colored coating film 82 having the same color as the undeteriorated portion 13 on the surface of the anticorrosive layer 18. The steel structure repair method of this modified example further includes a step of peeling off the release film 46 from the bonding layer 43. In this modified example, the steps of performing base preparation, forming the rust-preventive layer 18, forming the second colored coating film 82, peeling off the release film 46 from the bonding layer 43, covering the steel material 20 with the covering sheet 30, and forming the first colored coating film 81 are performed in this order.

[0224] As shown in Fig. 9A, a steel structure 100 to be repaired by the steel structure repair method of this modified example has a deteriorated portion 12 as described in the above embodiment, and an undeteriorated portion 13. The undeteriorated portion 13 is a portion of the steel structure 100 that is not the deteriorated portion 12. In the undeteriorated portion 13, an undeteriorated coating film 50 is located.

[0225] In the process of performing surface preparation on the deteriorated portion 12 of the steel structure 100, as shown in FIG. 9B, the deteriorated portion 12 of the steel structure 100 is subjected to surface preparation. At this time, the undeteriorated portion 13 surrounding the deteriorated portion 12 may also be subjected to surface preparation. The process of performing surface preparation on the deteriorated portion 12 of the steel structure 100 includes a process of performing one, two, or three types of scraping treatment on the deteriorated portion 12. At this time, the scraping treatment may also be performed on the undeteriorated portion 13 surrounding the deteriorated portion 12. FIG. 9B shows an example in which three types of scraping are performed on the deteriorated portion 12 and the undeteriorated portion 13 surrounding the deteriorated portion 12. The areas of the deteriorated portion 12 and the undeteriorated portion 13 that have been subjected to surface preparation become the repaired portion 10a shown in FIG. 7 and FIG. 8. The areas of the undeteriorated portion 13 that have not been subjected to surface preparation become the non-repaired portion 10b shown in FIG. 7 and FIG. 8.

[0226] In the step of forming the anti-rust layer 18, as shown in Fig. 9C, the anti-rust layer 18 is formed on the surface of the surface-prepared portion of the steel structure 100. The step of forming the anti-rust layer 18 in this modified example can be performed similarly to the step of forming the anti-rust layer 18 in the above-described embodiment. As an example, in this step, the anti-rust layer 18 is formed so as to cover the entire surface-prepared portion of the steel structure 100. As a result, in the repaired steel structure 10, the anti-rust layer 18 covers the entire portion of the steel material 20 located at the repaired portion 10a.

[0227] In the step of forming the second colored coating film 82, as shown in FIG. 9D, the second colored coating film 82 is formed on the surface of the anticorrosive layer 18 in the same color as the undeteriorated portion 13. The material of the second colored coating film 82 may be a conventionally known material for a coating film that displays a design. The method of forming the second colored coating film 82 may be a conventionally known method for forming a coating film that displays a design. As an example, in this step, the second colored coating film 82 is formed so as to cover the entire surface-prepared portion of the steel structure 100. As a result, in the repaired steel structure 10, the second colored coating film 82 covers the entire portion of the steel material 20 located at the repaired portion 10a.

[0228] In the steel structure repair method of this modified example, the covering sheet 30 used is the covering sheet 30 shown in Fig. 6 which further includes a bonding layer 43 and a release film 46 covering the bonding layer 43. In this case, a step of peeling off the release film 46 from the bonding layer 43 is performed to expose the bonding layer 43.

[0229] In the step of covering the steel material 20 with the covering sheet 30, as shown in FIG. 9E, the steel material 20 of the steel structure 100, which has been subjected to surface preparation, is covered with the covering sheet 30. In the steel structure repair method of this modified example, in the step of covering the steel material 20 of the steel structure 100, which has been subjected to surface preparation, with the covering sheet 30, the covering sheet 30 is joined to the steel material 20 using the bonding layer 43 exposed by peeling off the release film 46 from the bonding layer 43. As an example, in the step of covering the steel material 20 with the covering sheet 30, the covering sheet 30 is bonded to the second colored coating film 82 by the bonding layer 43. As a result, the covering sheet 30 is bonded to the steel material 20 via the anticorrosive layer 18 and the second colored coating film 82.

[0230] In the steel structure repair method of this modification, the covering sheet 30 covers at least a part of the surface-prepared portion of the steel structure 100. As a result, in the steel structure 10 after repair, the covering sheet 30 is located at least in a part of the repaired portion 10a. In particular, in the steel structure repair method of this modification, the covering sheet 30 covers the entire surface-prepared portion of the steel structure 100. As a result, in the steel structure 10 after repair, the covering sheet 30 is located in the entire repaired portion 10a. In particular, in this modification, the covering sheet 30 does not cover a part of the steel structure 100 that has not been surface-prepared. As a result, in the steel structure 10 after repair, the covering sheet 30 is not located in another part of the non-repaired portion 10b. The design layer 47 of the covering sheet 30 used in the steel structure repair method of this modification is a colored base material 471 colored the same color as the undeteriorated portion 13. As a result, in the repaired steel structure 10, the decorative layer 47 of the covering sheet 30 becomes a colored base material 471 that is colored the same color as the non-repaired portion 10b.

[0231] In the step of forming the first colored coating film 81, as shown in FIG. 9F, the first colored coating film 81 is formed in the same color as the undeteriorated portion 13 so as to cover the surface-prepared portion of the steel structure 100 and the covering sheet 30. As the material of the first colored coating film 81, a conventionally known material for a coating film that displays a design can be used. As the method for forming the first colored coating film 81, a conventionally known method for forming a coating film that displays a design can be used. As an example, in this step, the first colored coating film 81 is formed so as to cover the entire surface-prepared portion of the steel structure 100. As a result, in the repaired steel structure 10, the first colored coating film 81 covers the entire portion of the steel material 20 located at the repaired portion 10a.

[0232] The effects of the steel structure 10 of this modified example and the method for repairing a steel structure of this modified example will be described below. As shown in Fig. 9A, there are cases where it is required to repair a steel structure 100 in which only a portion is a deteriorated portion 12 and the remaining portion is an undeteriorated portion 13. In this case, the steel structure 100 can also be repaired by a method in which the entire steel structure 100 is subjected to a surface preparation and the entire steel structure 100 is covered with a covering sheet 30. However, this method increases the cost required for the repair and lengthens the time required for the repair.

[0233] In contrast, the steel structure repair method of this modified example includes a step of performing surface preparation for the deteriorated portion 12 of the steel structure 100, and a step of covering the steel material 20 of the steel structure 100 that has been surface-prepared with the covering sheet 30. According to this repair method, the deteriorated portion 12 of the steel structure 100 is subjected to surface preparation, and then at least a part of the surface-prepared portion of the steel structure 100 is covered with the covering sheet 30, thereby completing the repair. Therefore, the repair can be completed without performing surface preparation for the portion other than the deteriorated portion 12. Furthermore, the repair can be completed without covering the portion of the steel structure 100 that has not been surface-prepared with the covering sheet 30. As described above, according to the steel structure repair method of this modified example, the cost required for the repair can be reduced, and the time required for the repair can be shortened.

[0234] According to the above-mentioned method for repairing a steel structure of this modified example, it is possible to form a steel structure 10 of this modified example, which has a repaired portion 10a and a non-repaired portion 10b, with the covering sheet 30 located at least in a part of the repaired portion 10a. The steel structure 10 of this modified example can be formed while reducing the cost required for repair and shortening the time required for repair.

[0235] In the covering sheet 30 of this modification, the design layer 47 is a colored colored base material 471. Such a covering sheet 30 includes a base material 41 as a component separate from the design layer 47, and compared to a covering sheet 30 in which the design layer 47 is formed by printing or the like, the manufacturing process is shortened by the elimination of the process of forming the design layer 47 by printing or the like. Therefore, according to the above covering sheet 30, the productivity of the covering sheet 30 can be increased. Furthermore, since the design layer 47 is a colored colored base material 471, the thickness of the design layer 47 can be increased compared to the case in which the design layer 47 is formed by printing or the like. This allows the durability of the design layer 47 to be increased. Furthermore, the concealment property of the design layer 47 can be increased. This allows the design layer 47 to sufficiently block light, allowing the observer to more clearly see the color of the design layer 47 itself. From the viewpoint of facilitating the application of a complex design such as a pattern to the design layer 47, the design layer 47 formed by printing or the like is preferable to the design layer 47 which is a colored colored substrate 471. On the other hand, from the viewpoint of more easily forming the design layer 47 of a single color, the design layer 47 which is a colored colored substrate 471 is preferable to the design layer 47 formed by printing or the like. The above-mentioned covering sheet 30 can be used as the covering sheet 30 having the design layer 47 which is a colored substrate 471 colored in the same color as the undeteriorated portion 13 in the steel structure repair method of this modified example. The above-mentioned covering sheet 30 can be used as the covering sheet 30 having the design layer 47 which is a colored substrate 471 colored in the same color as the non-repaired portion 10b in the steel structure 10 of this modified example.

[0236] In the steel structure repair method of this modification, the steel structure 100 to be repaired has a deteriorated portion 12 and an undeteriorated portion 13. The design layer 47 of the covering sheet 30 is a colored base material 471 colored the same color as the undeteriorated portion 13. According to this repair method, the steel structure 100 can be repaired using the covering sheet 30 having the design layer 47, which is the colored base material 471. In particular, since the colored base material 471 is colored the same color as the undeteriorated portion 13, the repaired portion 10a where the covering sheet 30 is located and the non-repaired portion 10b where the covering sheet 30 is not located can be the same color in the repaired steel structure 10. This makes it possible to make the repaired portion 10a less noticeable in the repaired steel structure 10.

[0237] According to the above-mentioned repair method, a repaired steel structure 10 can be formed, which has a repaired portion 10a and a non-repaired portion 10b, the covering sheet 30 is located at least in a part of the repaired portion 10a, and the design layer 47 of the covering sheet 30 is a colored base material 471 colored the same color as the non-repaired portion 10b. In the steel structure 10, since the colored base material 471 is colored the same color as the non-repaired portion 10b, the repaired portion 10a where the covering sheet 30 is located and the non-repaired portion 10b where the covering sheet 30 is not located can be colored the same color. This makes it possible to make the repaired portion 10a less noticeable in the repaired steel structure 10.

[0238] According to the above-mentioned method for repairing a steel structure of this modified example, the deteriorated portion 12 of the steel structure 100 is subjected to surface preparation, and then at least a part of the surface-prepared portion of the steel structure 100 is covered with the covering sheet 30, thereby completing the repair. When carrying out such a repair method, from the viewpoint of making the repaired portion 10a less noticeable, it is preferable that the boundary between the design displayed by the coating film 50 or the like in the non-repaired portion 10b and the design displayed by the design layer 47 or the like in the repaired portion 10a is less noticeable. If the steel structure 10 and the steel structure 100 display a complex pattern in the non-repaired portion 10b and the undeteriorated portion 13, from the viewpoint of making the repaired portion 10a less noticeable, it is desirable to display a similar pattern in the design layer 47 and then adjust the joining position of the covering sheet 30. In this case, the joining position of the covering sheet 30 is adjusted so that the design displayed by the coating film 50 or the like in the non-repaired portion 10b and the undeteriorated portion 13 and the design displayed by the design layer 47 look continuous, making the repaired portion 10a less noticeable. In contrast, if the non-repaired portion 10b and the undeteriorated portion 13 are colored with a single color, the repaired portion 10a can be made less noticeable without the need to adjust the joining position of the covering sheet 30, simply by coloring the design layer 47 the same color as the non-repaired portion 10b and the undeteriorated portion 13. In particular, the design displayed by the coating film 50 or the like in the non-repaired portion 10b and the undeteriorated portion 13 and the design displayed by the design layer 47 look continuous, making the repaired portion 10a less noticeable. From the above, the steel structure repair method of this modified example is particularly suitable for repairing a steel structure 100 in which the undeteriorated portions 13 are colored a single color, and for repairing a steel structure 10 in which the non-repaired portions 10b are colored a single color.

[0239] Furthermore, when the non-repaired portion 10b and the undeteriorated portion 13 are given a single color, from the viewpoint of making the repaired portion 10a less noticeable, it is preferable that the design layer 47 is colored in the same single color as the non-repaired portion 10b and the undeteriorated portion 13. In addition, as described above, from the viewpoint of more easily forming the single-colored design layer 47, the design layer 47 which is the colored colored base material 471 is preferable to the design layer 47 formed by printing or the like. For this reason, the covering sheet 30 having the design layer 47 which is the colored colored base material 471 can be suitably applied in particular to the repair of the steel structure 100 in which the undeteriorated portion 13 is given a single color, and to the steel structure 10 in which the non-repaired portion 10b is given a single color.

[0240] The steel structure repair method of this modified example includes a step of forming a first colored coating film 81 of the same color as the undeteriorated portion 13 so as to cover the surface-prepared portion of the steel structure 100 and the covering sheet 30. According to the above-described repair method, it is possible to form a steel structure 10 having a first colored coating film 81 of the same color as the non-repaired portion 10b, which is formed so as to cover the portion of the steel material 20 located at the repair portion 10a and the covering sheet 30.

[0241] The steel structure repair method including a step of forming the first colored coating film 81, and the steel structure 10 including the first colored coating film 81, provide the following effects. The repaired steel structure 10 includes the first colored coating film 81 and the design layer 47. In this case, when the first colored coating film 81 peels off or becomes thin due to deterioration in the repaired portion 10a of the repaired steel structure 10, the design displayed by the design layer 47 can be displayed to an observer. Therefore, even if the repaired portion 10a of the repaired steel structure 10 deteriorates, the design can be displayed for a longer period in the repaired portion 10a.

[0242] In addition, if the steel structure repair method does not include a step of forming the first colored coating film 81 and the steel structure 10 does not include the first colored coating film 81, an observer who observes the repaired portion 10a of the steel structure 10 directly visually recognizes the design displayed by the design layer 47. In this case, even if the design layer 47 is colored the same color as the non-repaired portion 10b, the repaired portion 10a may be noticeable due to the difference in gloss between the design layer 47 and the non-repaired portion 10b. In particular, if the design layer 47 is a colored base material 471, the repaired portion 10a may be noticeable due to the difference in gloss between the colored base material 471 and the non-repaired portion 10b. In particular, the repaired portion 10a may be noticeable due to the difference in gloss between the design layer 47 and the coating film 50 located on the non-repaired portion 10b. In contrast, according to the steel structure repair method including the step of forming the first colored coating film 81, and the steel structure 10 including the first colored coating film 81, the gloss of the repaired portion 10a can be adjusted by the first colored coating film 81. This reduces the difference in gloss between the design layer 47 and the non-repaired portion 10b, making the repaired portion 10a less noticeable. In particular, as shown in Figures 7 and 8, by forming the first colored coating film 81 so that it covers a part of the portion of the steel material 20 that is located in the non-repaired portion 10b, the boundary between the repaired portion 10a and the non-repaired portion 10b can be made less noticeable, making the repaired portion 10a less noticeable.

[0243] The steel structure repair method of this modified example includes a step of forming an anticorrosive layer 18 on the surface of the base-prepared portion of the steel structure 100. According to the above-described repair method, it is possible to form a steel structure 10 having an anticorrosive layer 18 formed on the surface of the portion of the steel material 20 located in the repair portion 10a.

[0244] According to the steel structure repair method including the step of forming the rust-preventive layer 18, and the steel structure 10 including the rust-preventive layer 18, the rust-preventive layer 18 can reduce corrosion of the steel material 20.

[0245] The steel structure repair method of this modified example includes a step of forming a second colored coating film 82 of the same color as the undeteriorated portion 13 on the surface of the anticorrosive layer 18. According to the above-mentioned repair method, a steel structure 10 including the second colored coating film 82 formed on the surface of the anticorrosive layer 18 can be formed.

[0246] The steel structure repair method including the step of forming the second colored coating film 82 and the steel structure 10 including the second colored coating film 82 provide the following effects. The repaired steel structure 10 includes the second colored coating film 82 and the design layer 47. In this case, when the design layer 47 peels off or becomes thin due to deterioration in the repaired portion 10a of the steel structure 10 after the repair, the design displayed by the second colored coating film 82 can be displayed to an observer. Therefore, even if the repaired portion 10a of the steel structure 10 after the repair deteriorates, the design can be displayed for a longer period in the repaired portion 10a. From the viewpoint of displaying the design for a longer period in the repaired portion 10a, it is more preferable that the steel structure repair method includes the step of forming the first colored coating film 81 and the step of forming the second colored coating film 82. From the viewpoint of displaying the design in the repaired portion 10a for a longer period of time, it is more preferable that the steel structure 10 be provided with the first colored coating film 81 and the second colored coating film 82.

[0247] In the steel structure repair method of this modified example, the covering sheet 30 may include a bonding layer 43 and a release film 46 that covers the bonding layer 43. The steel structure repair method of this modified example may include a step of peeling the release film 46 from the bonding layer 43. In the steel structure repair method of this modified example, in the step of covering the steel material 20 of the steel structure 100 whose base material has been adjusted with the covering sheet 30, the covering sheet 30 may be bonded to the steel material 20 using the bonding layer 43 exposed by peeling the release film 46 from the bonding layer 43. According to the above-mentioned repair method, the bonding layer 43 can be protected from foreign matter such as dust by the release film 46 until the covering sheet 30 is bonded to the steel material 20 using the bonding layer 43.

[0248] In the steel structure repair method of this modified example, the step of performing surface preparation on the deteriorated portion 12 of the steel structure 100 includes a step of performing one, two, or three types of scraping treatment on the deteriorated portion 12. According to the above-mentioned repair method, defective portions of the old paint film 50 can be sufficiently removed.

[0249] The steel structure repair method of this modification may not include a step of forming the second colored coating film 82. In this case, in the step of covering the steel material 20 with the covering sheet 30, the covering sheet 30 may be joined to the anticorrosive layer 18 by the bonding layer 43. According to such a repair method, the steel structure 10 shown in FIG. 10 is formed. The steel structure 10 of this modification may not include the second colored coating film 82 as shown in FIG. 10. In this case, although not shown, the covering sheet 30 may be joined to the anticorrosive layer 18 by the bonding layer 43. However, from the viewpoint of displaying the design for a longer period in the repaired portion 10a, it is more preferable that the steel structure repair method includes a step of forming the second colored coating film 82. From the viewpoint of displaying the design for a longer period in the repaired portion 10a, it is more preferable that the steel structure 10 includes the second colored coating film 82.

[0250] The steel structure repair method of this modified example may not include a step of forming the first colored coating film 81. According to a repair method that does not include a step of forming the first colored coating film 81 and a step of forming the second colored coating film 82, a steel structure 10 shown in FIG. 11 is formed. The steel structure 10 of this modified example may not include the first colored coating film 81 as shown in FIG. 11. However, from the viewpoint of reducing the difference in gloss between the design layer 47 and the non-repaired portion 10b, making the repaired portion 10a less noticeable, and displaying the design for a longer period in the repaired portion 10a, it is more preferable that the steel structure repair method includes a step of forming the first colored coating film 81. From the viewpoint of reducing the difference in gloss between the design layer 47 and the non-repaired portion 10b, making the repaired portion 10a less noticeable, and displaying the design for a longer period in the repaired portion 10a, it is more preferable that the steel structure 10 includes the first colored coating film 81.

[0251] The covering sheet 30 of this modification may cover the steel material 20 of the steel structure 100 that does not have the deteriorated portion 12 and the repaired portion 10a and has not been subjected to surface preparation. The covering sheet 30 of this modification may cover the coating film 50 of the steel structure 100 that does not have the deteriorated portion 12 and the repaired portion 10a and has not been subjected to surface preparation, which includes a colored coating film as the coating film 50. In this case, the covering sheet 30 may be joined to the coating film 50 using the bonding layer 43. In this case, the colored coating film may be formed so as to cover the covering sheet 30. The material and the forming method of the colored coating film that covers the covering sheet 30 may be the same as the material and the forming method of the first colored coating film 81 described above. The coating film 50 of the steel structure 100 in this case may include a colored coating film and an anti-corrosive layer. The material and the forming method of the colored coating film included in the coating film 50 may be the same as the material and the forming method of the second colored coating film 82 described above. The material and the forming method of the anticorrosive layer included in the coating film 50 can be the same as the material and the forming method of the anticorrosive layer 18 described above. The steel structure 100 may include multiple coating films 50 as shown in FIG. 5 and described above. When the covering sheet 30 of this modification covers the coating film 50 of the steel structure 100 including a colored coating film as the coating film 50, the design layer 47 can be colored the same color as the colored coating film as the coating film 50. This can reduce the difference in appearance between the part of the coating film 50 covered by the covering sheet 30 and the part of the coating film 50 that is not covered. Therefore, while a part of the coating film 50 is covered by the covering sheet 30, the part of the coating film 50 covered by the covering sheet 30 can be made less noticeable. EXAMPLES

[0252] The present disclosure will be described in more detail with reference to examples, but the present disclosure is not limited to the following examples.

[0253] <<<1. Preparation of covering sheet>>> Covering sheets according to Examples 1 to 3 and Comparative Example 1 were produced.

[0254] <<Example 1>> 2B was produced as the covering sheet 30 according to Example 1. That is, the covering sheet 30 included a barrier layer 44, a bonding layer 491, a substrate 41, a design layer 47, a bonding layer 492, a transparent resin layer 48, and a weather-resistant layer 42 in this order from the second surface 32 to the first surface 31 in the stacking direction.

[0255] A polypropylene sheet having a thickness of 60 μm and having been subjected to a corona discharge treatment on both sides was used as the substrate 41. The substrate 41 was brown in color.

[0256] Next, a design layer 47 displaying a wood grain pattern was formed on one side of the substrate 41. The design layer 47 was formed by applying a printing ink containing a two-component curing acrylic-urethane resin and a colorant by gravure printing. The thickness of the design layer 47 was 3 μm.

[0257] Next, a bonding layer 492 was formed on the design layer 47. The bonding layer 492 was formed by applying a transparent urethane resin adhesive onto the design layer 47 and drying it. The thickness of the bonding layer 492 was 3 μm.

[0258] Next, a transparent resin layer 48 was formed on the bonding layer 492 by forming a sheet of transparent polypropylene. The transparent resin layer 48 had a thickness of 80 μm. The polypropylene was formed into a sheet by extrusion processing using an extruder at an extrusion temperature of 235° C. The take-up speed of the extruded sheet was adjusted so that the transparent resin layer 48 to be produced had a thickness of 80 μm.

[0259] Next, a corona discharge treatment was applied to one surface of the transparent resin layer 48. Thereafter, a primer layer was formed on the corona discharge treated surface of the transparent resin layer 48 using a resin composition for a primer layer.

[0260] The resin composition for the primer layer was prepared by mixing 100 parts by mass of the mixture, 5 parts by mass of a curing agent, 20 parts by mass of an ultraviolet absorber, and a diluting solvent. The 100 parts by mass of the mixture was a mixture of a polycarbonate-based urethane-acrylic copolymer and an acrylic polyol. The 5 parts by mass of the curing agent was hexamethylene diisocyanate.

[0261] The primer layer resin composition was applied by gravure printing to the corona discharge treated surface of the transparent resin layer 48. The primer layer was obtained by drying the coating of the primer layer resin composition formed on the transparent resin layer 48. The thickness of the primer layer was 4 μm.

[0262] Next, a weather-resistant layer 42 was formed on the primer layer using an ionizing radiation curable resin composition. The ionizing radiation curable resin composition was prepared by mixing 100 parts by mass of a urethane acrylate oligomer, 4 parts by mass of a hydroxyphenyl triazine-based ultraviolet absorber as an ultraviolet absorber, and 3 parts by mass of a hindered amine-based non-reactive light stabilizer. The prepared ionizing radiation curable resin composition was applied onto the primer layer to form an uncured resin layer on the primer layer.

[0263] Thereafter, the uncured resin layer was cured by irradiating the uncured resin layer with an electron beam. The conditions for the electron beam irradiation were an acceleration voltage of 165 kV and an irradiation dose of 5 Mrad (50 kGy). A weather-resistant layer 42 having a thickness of 5 μm was formed by irradiating the uncured resin layer with an electron beam. The weather-resistant layer 42 and the transparent resin layer 48 were bonded together via a primer layer not shown in FIG. 2B.

[0264] Furthermore, a transparent urethane resin-based adhesive was applied to the surface of the substrate 41 opposite to the surface on which the design layer 47, the bonding layer 492, the transparent resin layer 48, the primer layer and the weather-resistant layer 42 were formed, and then dried to form a bonding layer 491 having a thickness of 3 μm.

[0265] Furthermore, a barrier film 44X including a barrier layer 44 was prepared. A vapor deposition film included in IB-PET-UB (manufactured by Dai Nippon Printing Co., Ltd.) was used as the barrier layer 44. It can be said that IB-PET-UB is a barrier film 44X including a resin film 44a made of polyethylene terephthalate and a barrier layer 44 which is a vapor deposition film. Next, the substrate 41 and the barrier film 44X were bonded by dry lamination via the bonding layer 491. At this time, the substrate 41 and the barrier film 44X were bonded so that the surface of the barrier film 44X formed by the barrier layer 44 and the surface of the substrate 41 faced each other.

[0266] As a result, the covering sheet 30 according to Example 1 was obtained, which included, in the stacking direction from the second surface 32 to the first surface 31, the barrier film 44X, the bonding layer 491, the substrate 41, the design layer 47, the bonding layer 492, the transparent resin layer 48, the primer layer, and the weather-resistant layer 42. Since the barrier film 44X includes the barrier layer 44, the covering sheet 30 according to Example 1 included, in the stacking direction from the second surface 32 to the first surface 31, the barrier layer 44, the bonding layer 491, the substrate 41, the design layer 47, the bonding layer 492, the transparent resin layer 48, the primer layer, and the weather-resistant layer 42.

[0267] <<Example 2>> 2C was produced as the cover sheet according to Example 2. That is, the cover sheet 30 included a base material 41, a design layer 47, a bonding layer 493, a barrier layer 44, a bonding layer 494, a transparent resin layer 48, and a weather-resistant layer 42 in this order from the second surface 32 to the first surface 31 in the stacking direction.

[0268] In Example 2, the substrate 41 and the design layer 47 were produced by a method similar to that used to produce the substrate 41 and the design layer 47 in Example 1. Then, the bonding layer 493 was formed on the design layer 47 by a method similar to that used to form the bonding layer 492 on the design layer 47 in Example 1.

[0269] Next, a barrier film 44X including a resin film 44a and a barrier layer 44 was prepared similar to that of Example 1. Next, the design layer 47 and the barrier film 44X were bonded by dry lamination via the bonding layer 493. At this time, the design layer 47 and the barrier film 44X were bonded such that the surface of the barrier film 44X formed by the barrier layer 44 and the surface of the design layer 47 faced each other.

[0270] Next, a corona discharge treatment was performed on the surface of the barrier film 44X that was made of the resin film 44a. Then, an adhesive layer 494 was formed on the resin film 44a by the same method as that used to form the adhesive layer 492 on the design layer 47 in Example 1.

[0271] Next, the transparent resin layer 48, the primer layer, and the weather-resistant layer 42 were formed on the bonding layer 494 by the same method as the method for forming the transparent resin layer 48, the primer layer, and the weather-resistant layer 42 on the bonding layer 492 in Example 1. The weather-resistant layer 42 and the transparent resin layer 48 were bonded via a primer layer not shown in FIG. 2C.

[0272] As a result, a covering sheet 30 according to Example 2 was obtained, which included, in the stacking direction from the second surface 32 to the first surface 31, the base material 41, the design layer 47, the bonding layer 493, the barrier film 44X, the bonding layer 494, the transparent resin layer 48, the primer layer, and the weather-resistant layer 42. Since the barrier film 44X includes the barrier layer 44, the covering sheet 30 according to Example 2 included, in the stacking direction from the second surface 32 to the first surface 31, the base material 41, the design layer 47, the bonding layer 493, the barrier layer 44, the bonding layer 494, the transparent resin layer 48, the primer layer, and the weather-resistant layer 42.

[0273] <<Example 3>> As the covering sheet 30 according to Example 3, a covering sheet 30 similar to that of Example 1 was produced except for the following points. The covering sheet 30 according to Example 3 did not include the transparent resin layer 48 and the bonding layer 492. In the covering sheet 30 according to Example 3, the design layer 47 and the primer layer were in direct contact with each other. In the covering sheet 30 according to Example 3, the design layer 47 was a colored substrate 471. The covering sheet 30 according to Example 3 did not include a substrate 41 as a component separate from the design layer 47.

[0274] In Example 3, a primer layer and a weather-resistant layer 42 were formed on the design layer 47, which is the colored substrate 471, by a method similar to the method of forming the primer layer and the weather-resistant layer 42 on the transparent resin layer 48 in Example 1. Furthermore, a barrier film 44X was prepared by a method similar to the method of preparing a barrier film 44X and bonding the substrate 41 and the barrier film 44X via a bonding layer 492 in Example 1, and the design layer 47, which is the colored substrate 471, and the barrier film 44X were bonded via the bonding layer 492.

[0275] As a result of the above, a covering sheet 30 according to Example 3 was obtained, which includes, in the stacking direction from the second surface 32 to the first surface 31, a barrier layer 44, a bonding layer 491, a design layer 47 which is a colored base material 471, a primer layer, and a weather-resistant layer 42.

[0276] <<Comparative Example 1>> A covering sheet according to Comparative Example 1 was prepared similarly to covering sheet 30 according to Example 1, except that it did not include barrier film 44X and bonding layer 491. The covering sheet according to Comparative Example 1 included, in this order from the second surface to the first surface in the stacking direction, a base material, a design layer, a bonding layer bonding the design layer and the transparent resin layer, a transparent resin layer, a primer layer, and a weather-resistant layer.

[0277] <<<2. Measurement and Evaluation>>> Measurement and evaluation of the covering sheets according to the examples and comparative examples were carried out as described below. The samples used for the measurement and evaluation were visually inspected for the absence of any abnormalities such as dust or scratches.

[0278] <<2-1. Water vapor permeability>> The water vapor permeability of the covering sheets according to the examples and comparative examples was measured in accordance with JIS K7129-2:2019 under an environment of temperature 40°C and humidity 90% RH. The water vapor permeability was measured using a "PERMATRAN-w 3 / 33" manufactured by MOCON, USA. The measured water vapor permeability was 3.0 g / (m 2 We evaluated whether the time to delivery was less than 1 day.

[0279] <<2-2. Oxygen permeability>> The oxygen permeability of the covering sheets according to the examples and comparative examples was measured in an environment of temperature 23°C and humidity 60% RH in accordance with JIS K7126-2:2006 "Appendix A (Regulations): Test method for oxygen gas permeability by electrolytic sensor method". The oxygen permeability was measured using an "OX-TRAN 2 / 20" manufactured by MOCON, USA. The measured oxygen permeability was 6.57 cm 3 / (m 2 We evaluated whether the time to delivery was less than 1 day.

[0280] <<2-3. Weather resistance test>> A steel material with an anticorrosive layer formed thereon was prepared as shown in FIG. 1C. The material of the anticorrosive layer was Sabishut manufactured by Dai Nippon Toryo Co., Ltd. Then, the coating sheet to be measured was bonded to the anticorrosive layer. At this time, the coating sheet and the anticorrosive layer were bonded to each other via an acrylic adhesive so that the surface of the anticorrosive layer and the second surface of the coating sheet faced each other. The thickness of the acrylic adhesive layer bonding the coating sheet and the anticorrosive layer was 80 μm. In this manner, an evaluation sample was prepared.

[0281] The above-mentioned weather resistance test for 408 hours was carried out on the evaluation samples of each example. The weather resistance test was carried out under the following conditions.

[0282] A 20-hour irradiation process and a 4-hour condensation process were counted as one cycle, and the evaluation sample was exposed to the irradiation process and the condensation process until the cycle reached 408 hours. A 30-second shower process was carried out after the irradiation process and before the condensation process started, and after the condensation process and before the irradiation process started. In the shower process, the evaluation sample held in the weather resistance test device was showered with water.

[0283] The weather resistance test device used was the ultra-accelerated weather resistance test device "Eye Super UV Tester SUV-W261" manufactured by Iwasaki Electric Co., Ltd. The UV lamp, lamp jacket, and illuminometer included in the weather resistance test device were as follows. UV lamp: Product name: M04-L21WB / SUV, manufactured by Iwasaki Electric Co., Ltd. Lamp jacket: Product name: WJ50-SUV, manufactured by Iwasaki Electric Co., Ltd. Illuminance meter: Product name: UVD-365PD, manufactured by Iwasaki Electric Co., Ltd.

[0284] The conditions for the irradiation step were as follows: <Irradiation conditions> Black panel temperature: 63℃ ·Illuminance: 100mW / cm 2 ·Battle humidity: 50%RH Duration: 20 hours

[0285] The conditions for the condensation process were as follows: <Condensation conditions> ·Illuminance: 0mW / cm 2 ·Battle humidity: 98%RH Duration: 4 hours

[0286] The color difference ΔE of the anti-rust layer was measured before and after the weather resistance test. The measured color difference ΔE is L defined in JIS Z8781:2013. * a * b * In the color system, the color before the weather resistance test is L * 1a * 1b * 1. The color after weather resistance test* 2a * 2b * The color L before the weather resistance test is defined by the above formulas (1) to (4). * 1a * 1b * 1, and color L after weather resistance test * 2a * 2b * The color 2 was the color of the anticorrosive layer observed through the covering sheet from the first surface side of the covering sheet. The measured color difference ΔE was evaluated as being 4 or less.

[0287] The results of <<2-1. Water vapor permeability>>, <<2-2. Oxygen permeability>> and <<2-3. Weather resistance test>> are shown in Table 1. In the "Water vapor permeability" column of Table 1, the results of the water vapor permeability test show that the water vapor permeability was 3.0 g / (m 2 ·day) or less is rated "A", and 3.0g / (m 2 ·day), it is described as "B". In the "Oxygen permeability" column of Table 1, the results of the oxygen permeability test show that the oxygen permeability was 6.57 cm 3 / (m 2 If it is less than 6.57cm, it is rated "A" 3 / (m 2 In the "Color Difference ΔE" column, if the color difference ΔE was 4 or less as a result of the weather resistance test, an "A" was entered.

[0288] [Table 1]

[0289] In the covering sheets of Examples 1 to 3, which included a barrier layer, both the water vapor permeability and the oxygen permeability were rated as "A." In contrast, in the covering sheet of Comparative Example 1, which did not include a barrier layer, both the water vapor permeability and the oxygen permeability were rated as "B." These results suggest that the inclusion of a barrier layer in the covering sheet increases the water vapor permeability to 3.0 g / (m 2 ·day) or less, and the oxygen permeability can be reduced to 6.57 cm 3 / (m2 It was found that this can be done in less than 10 minutes.

[0290] The color difference ΔE was also evaluated as “A” for the covering sheets of Examples 1 to 3. This shows that the covering sheets of Examples 1 and 2 can suppress discoloration of the anticorrosive layer due to ultraviolet rays. [Explanation of symbols]

[0291] 10: steel structure, 11: surface, 12: deteriorated part, 15: bonding layer, 18: anti-rust layer, 19: top coat layer, 20: steel material, 22: surface preparation surface, 30: covering sheet, 31: first surface, 32: second surface, 41: substrate, 42: weather-resistant layer, 43: bonding layer, 44: barrier layer, 46: release film, 50: coating film, 50P: active film, 51: anti-rust layer, 52: first undercoat layer, 53: second undercoat layer, 54: intermediate coat layer, 55: top coat layer, 60: rust, 100: steel structure

Claims

1. A coating sheet used to coat steel materials, The film includes a barrier layer, a design layer, and a weather-resistant layer, The cover sheet has a maximum spectral transmittance of 1.0% or less at a wavelength of 300 nm or more and 350 nm or less.

2. A first surface facing away from the steel material and a second surface facing the steel material, The application sheet according to claim 1 , wherein a distance between the barrier layer and the second surface is smaller than a distance between the design layer and the second surface.

3. Further comprising a substrate, The covering sheet according to claim 2 , wherein a distance between the barrier layer and the second surface is smaller than a distance between the weather-resistant layer and the second surface, and is also smaller than a distance between the substrate and the second surface.

4. Further comprising a transparent resin layer, The covering sheet according to claim 3 , wherein the barrier layer, the substrate, the design layer, the transparent resin layer, and the weather-resistant layer are laminated in this order from the second surface to the first surface.

5. 2. The covering sheet according to claim 1, wherein when an anticorrosive layer is formed on a surface of the steel material, the surface of the steel material on which the anticorrosive layer is formed is covered with the covering sheet, and a weather resistance test is performed for 408 hours, a color difference ΔE of the anticorrosive layer before and after the weather resistance test is 4 or less.

6. The water vapor permeability at a temperature of 40°C and a humidity of 90% RH is 3.0 g / (m ２ 2. The covering sheet according to claim 1, wherein the average surface area per unit area is 100 mm or less.

7. The oxygen permeability at a temperature of 23°C and a humidity of 60% is 6.57 cm ３ / (m ２ 2. The covering sheet according to claim 1, wherein the average surface area per unit area is 100 mm or less.

8. The covering sheet according to claim 1 , wherein the weather-resistant layer comprises an ultraviolet absorbing agent and a light stabilizer.

9. A first surface facing away from the steel material and a second surface facing the steel material, The application sheet according to claim 1 , comprising, in this order from the second surface to the first surface, a bonding layer constituting the second surface, and a substrate.

10. The application sheet according to claim 1 , wherein the design layer is a colored base material.

11. The steel material; A steel structure comprising the covering sheet according to any one of claims 1 to 10.

12. The steel structure has a repaired portion and a non-repaired portion, The covering sheet is positioned on at least a portion of the repaired portion, The steel structure according to claim 11 , wherein the decorative layer of the covering sheet is a colored base material colored the same color as the non-repaired portion.

13. The steel structure according to claim 12, further comprising a first colored coating film having the same color as the non-repaired portion and formed so as to cover the portion of the steel material located in the repaired portion and the covering sheet.

14. The steel structure according to claim 12, further comprising an anti-corrosion layer formed on a surface of the portion of the steel material located in the repaired portion.

15. The steel structure according to claim 14, further comprising a second colored coating film formed on a surface of the anticorrosive layer.

16. A process of performing base preparation for deteriorated parts of a steel structure; A method for repairing a steel structure, comprising: a step of covering the steel material of the steel structure, the base of which has been conditioned, with the covering sheet according to any one of claims 1 to 10.

17. The steel structure has the deteriorated portion and a non-deteriorated portion, The method for repairing a steel structure according to claim 16, wherein the decorative layer of the covering sheet is a colored base material colored the same color as the undeteriorated portion.

18. 18. The method for repairing a steel structure according to claim 17, further comprising the step of forming a first colored coating film having the same color as the undeteriorated portion so as to cover the surface-prepared portion of the steel structure and the covering sheet.

19. The method for repairing a steel structure according to claim 17, further comprising the step of forming an anti-corrosive layer on a surface of the surface-prepared portion of the steel structure.

20. The method for repairing a steel structure according to claim 19, further comprising the step of forming a second colored coating film having the same color as the undeteriorated portion on a surface of the anticorrosive layer.

21. The covering sheet further includes a bonding layer and a release film covering the bonding layer, The steel structure repair method further includes a step of peeling off the release film from the bonding layer, 17. The method for repairing a steel structure according to claim 16, wherein in the process of covering the steel material of the steel structure whose base surface has been adjusted with the covering sheet, the covering sheet is joined to the steel material using the bonding layer exposed by peeling off the release film from the bonding layer.

22. 17. The method for repairing a steel structure according to claim 16, wherein the step of performing surface preparation on the deteriorated portion of the steel structure includes a step of performing one, two or three types of scraping treatment on the deteriorated portion.

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