Decorative steel plate and method for producing decorative steel plate

Abstract

To provide a decorative steel plate with superior touch sensation and a method for producing a decorative steel plate.SOLUTION: A decorative steel plate 10 includes: a plated steel plate layer 1; a base coat layer 4 provided on the upper side UP of the plated steel plate layer 1; a pattern layer 5 provided on the upper side UP of the base coat layer 4; and a surface protective layer 6 with a thickness of 5 μm or more, having an uneven shape on the upper side UP surface, and provided on the upper side of the pattern layer. In the uneven shape of the surface protective layer 6, the ratio of the cutting level difference Rdc to the thickness of the surface protective layer 6 is 0.1 or more and 0.2 or less.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a decorative steel sheet and a method for manufacturing the decorative steel sheet. [Background technology]

[0002] Conventionally, there are decorative materials used for surface decoration of building materials such as interior materials and exterior walls of buildings such as houses, fixtures, etc. Such decorative materials include decorative steel sheets using steel sheets such as plated steel sheets, and decorative paper using paper base materials such as titanium paper.

[0003] Decorative materials such as decorative steel sheets and decorative papers are required to have durability so as not to impair the beauty of their surfaces even when used for a long period of time. In particular, decorative steel sheets used for the surface decoration of entrance doors of detached houses, condominiums, apartments, etc., and for the surface decoration of exterior walls of buildings are required to have weather resistance such as corrosion resistance.

[0004] In addition, methods for imparting a desired feel to the surface of decorative steel sheets include forming an uneven shape on the surface by embossing using an embossing plate, and forming an uneven shape on the surface by using aggregate added to a specific layer (e.g., a base coat layer) that forms the decorative material.

[0005] An example of a decorative steel sheet having a base coat layer to which aggregate is added is a printed steel sheet described in Patent Document 1. The printed steel sheet described in Patent Document 1 has a primer layer, a base coat layer, a pattern printed layer, and a top coat layer, in that order, on one side of a plated steel sheet that has been subjected to a chemical conversion treatment, and the base coat layer contains aggregate.

[0006] There are also decorative steel sheets in which a matting agent such as silica or talc is added to the protective layer provided on the surface to impart a matte finish. The matting agent is made of particles of irregular shape having irregular corners and edges, and some of these particles are made to protrude from the average surface of the protective layer to form a fine uneven shape, thereby imparting a matte finish. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Patent Publication No. 2021-11052 Summary of the Invention [Problem to be solved by the invention]

[0008] However, when adding aggregate to the base coat layer and printing a pattern on the top of it, the surface having the uneven shape due to the aggregate is printed by a method such as gravure printing or offset printing, so there is a risk of poor print reproducibility. In addition, when forming the uneven shape using an embossing plate, a process for embossing is required, which takes time to produce and may result in poor productivity. In addition, a plate-making process for creating the embossing plate is also required.

[0009] Furthermore, when realizing a desired texture or delicate feel by using an uneven shape formed with an embossing plate, it is necessary to create several types of embossing plates, form an uneven shape on the surface of a decorative steel sheet with each embossing plate, and then evaluate the feel of each decorative steel sheet to determine the desired texture and feel, which is a process that must be repeated multiple times, which can be time-consuming.

[0010] Furthermore, when a matting agent is added to the protective layer that forms the surface of the decorative steel sheet to achieve the desired low gloss (low luster), it is generally necessary to add a large amount of matting agent to the protective layer. In this case, when an object or the like comes into contact with the surface of the decorative steel sheet, there is a risk that the particles added as the matting agent will fall off due to the contact of the object or the like. Furthermore, the fallen particles may rub against the surface of the protective layer, causing scratches on the surface of the decorative steel sheet and changing the surface shape of the protective layer, resulting in a change in the gloss of the surface of the decorative steel sheet and a decrease in the aesthetic appearance, which may result in poor design. Furthermore, if a large amount of matting agent is added, the protective layer may become cloudy, making it difficult to see the pattern provided under the protective layer.

[0011] In view of the above circumstances, an object of the present invention is to provide a decorative steel sheet having an excellent feel to the touch and a method for manufacturing the decorative steel sheet. [Means for solving the problem]

[0012] In order to solve the above problems, the present invention proposes the following means. The decorative steel sheet of the present invention comprises a plated steel sheet layer, a base coat layer provided on the upper side of the plated steel sheet layer, a pattern layer provided on the upper side of the base coat layer, and a surface protective layer provided on the upper side of the pattern layer, the surface having an uneven shape, a thickness of 5 μm or more, and wherein the uneven shape of the surface protective layer has a ratio of cut level difference Rdc to the thickness of the surface protective layer of 0.1 or more and 0.2 or less.

[0013] In the decorative steel sheet described above, the plated steel sheet layer may have a steel sheet layer and a chemical conversion treatment layer provided on the upper side of the steel sheet layer.

[0014] The decorative steel sheet may further include a primer layer provided on the upper side of the plated steel sheet layer.

[0015] In the decorative steel sheet, the surface protective layer may have a thickness of 18 μm or less and contain particles having an average particle size of 3 μm or more and 11 μm or less.

[0016] In the decorative steel sheet, the surface protective layer may have a 60 degree reflected gloss of 10.0 or less.

[0017] In the above-mentioned decorative steel sheet, the uneven shape of the surface protective layer has a plurality of ridge-like portions that rise in a ridge-like manner and are adjacent to each other in the width direction, and the plurality of ridge-like portions adjacent to each other in the width direction may have a sinusoidal shape in a cross section parallel to the vertical direction.

[0018] In the decorative steel sheet, the surface protective layer may contain an ionizing radiation curable resin.

[0019] In the decorative steel sheet, the plated steel sheet layer may include a zinc-plated steel sheet or an aluminum-zinc alloy-plated steel sheet.

[0020] The manufacturing method of the decorative steel sheet of the present invention includes a protective layer application process for forming a surface protective layer having a thickness of 5 μm or more on the upper side of a plated steel sheet layer, and a first irradiation process for irradiating the surface of the surface protective layer with light having a wavelength of 200 nm or less to form an uneven shape so that the ratio of the cut level difference Rdc to the thickness of the surface protective layer is 0.1 or more and 0.2 or less. Effect of the Invention

[0021] According to the decorative steel sheet and the manufacturing method of the decorative steel sheet of the present invention, it is possible to provide a decorative steel sheet and a manufacturing method of the decorative steel sheet having an excellent feel to the touch. [Brief description of the drawings]

[0022] [Figure 1] 1 is a cross-sectional view that illustrates a schematic diagram of a decorative steel sheet according to an embodiment of the present invention. [Diagram 2] 3 is a photograph showing an example of the uneven shape of the decorative steel sheet. [Diagram 3] FIG. 2 is a cross-sectional view showing a schematic view of a surface protective layer of the decorative steel sheet. [Figure 4] 3 is a flowchart showing an example of a method for manufacturing the decorative steel sheet. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] An embodiment of the present invention will be described with reference to the drawings.

[0024] FIG. 1 is a cross-sectional view that typically shows a decorative steel sheet 10 according to this embodiment. In this embodiment, as shown in Figure 1, the thickness direction of the decorative steel plate 10 is defined as the "vertical direction V", the direction in which the surface protective layer 6 of the decorative steel plate 10 is provided is defined as the "upper side UP" in the vertical direction V, and the opposite direction is defined as the "lower side LO" in the vertical direction V.

[0025] The decorative steel sheet 10 comprises a plated steel sheet layer 1, a back surface coating layer 2, a primer layer 3, a base coating layer 4, a design layer 5, and a surface protective layer 6.

[0026] The plated steel sheet layer 1 is a layer provided on the upper side UP of the back surface coating layer 2. The plated steel sheet layer 1 has a steel sheet layer 1a, a first chemical conversion treatment layer 1b provided on the upper side UP of the steel sheet layer 1a, and a second chemical conversion treatment layer 1c provided on the lower side LO of the steel sheet layer 1a.

[0027] For the steel sheet layer 1a, known steel sheets such as zinc-plated steel sheets and aluminum-zinc alloy-plated steel sheets can be used. The plated steel sheet layer 1 is formed, for example, by subjecting a zinc-plated steel sheet having a zinc plating (metal coating) formed on the surface of the steel sheet by hot-dip galvanizing or the like to a chemical conversion treatment such as a chromate-free treatment.

[0028] The first chemical conversion treatment layer 1b and the second chemical conversion treatment layer 1c are layers formed by this chemical conversion treatment, and contain iron-zinc-based intermetallic compounds generated by the chemical conversion treatment. Hereinafter, the first chemical conversion treatment layer 1b and the second chemical conversion treatment layer 1c may be simply referred to as the chemical conversion treatment layer.

[0029] The back surface coating layer 2 is a layer provided on the lower side LO of the decorative steel plate 10. A resin paint mainly composed of an epoxy resin or a polyester resin can be used as the back surface coating layer 2. A rust inhibitor may be added to the back surface coating layer 2 to improve corrosion resistance.

[0030] The back surface coating layer 2 is formed, for example, by applying a resin paint that forms the back surface coating layer 2 using a known printing method such as gravure printing, offset printing, flexographic printing, silk screen printing, or inkjet printing, or using a known coating device, and then heating and baking the applied paint.

[0031] The primer layer 3 is a layer provided on the upper side UP of the plated steel sheet layer 1. A known resin paint for primers can be used for the primer layer 3. Examples of the resin paint used for the primer layer 3 include known curable paints containing thermosetting resins such as polyester resin, urethane resin, epoxy resin, melamine resin, alkyd resin, phenol resin, and acrylic resin.

[0032] The resin paint forming the primer layer 3 may mainly contain a polyester resin, an organic additive, and a pigment. In this case, the composition ratio of the main raw materials of the resin paint forming the primer layer 3 may be about 57 parts by mass of the polyester resin, about 1 part by mass of the organic additive, and about 42 parts by mass of the pigment, when the resin paint is taken as 100 parts by mass. Moreover, the resin coating material forming the primer layer 3 may contain an anti-rust pigment in order to improve corrosion resistance.

[0033] The primer layer 3 is formed, for example, by applying a resin coating material for forming the primer layer 3 using a known printing method such as gravure printing, offset printing, flexographic printing, silk screen printing, or inkjet printing, or using a known coating device, and then baking the applied material. The thickness of the primer layer 3 is preferably 0.5 μm or more and 10.0 μm or less.

[0034] The base coat layer 4 is a layer provided on the upper side UP of the primer layer 3. The base coat layer 4 is a monochromatic coat layer that serves as the base for the overall color tone of the decorative steel sheet 10. For the base coat layer 4, a paint containing a known binder resin for base coats can be used.

[0035] The base coat layer 4 is formed, for example, by applying a resin paint that forms the base coat layer 4 using a known printing method such as gravure printing, offset printing, flexographic printing, silk screen printing, or inkjet printing, or using a known coating device, and then heating and baking the applied paint.

[0036] As the binder resin forming the base coat layer 4, for example, a thermosetting resin such as a polyester resin, a urethane resin, an epoxy resin, a melamine resin, an alkyd resin, a phenol resin, or an acrylic resin can be used. From the viewpoint of processability, it is preferable to use a polyester-based resin as the main resin for the binder resin forming the base coat layer 4. In addition, a pigment is added to the resin paint forming the base coat layer 4, for example, to achieve a monochromatic color tone.

[0037] The resin paint forming the base coat layer 4 may contain polyester-based resin, melamine-based resin, and pigment as main raw materials. In this case, the composition ratio of the main raw materials of the resin paint forming the base coat layer 4 may be about 45 parts by mass of polyester-based resin, about 15 parts by mass of melamine-based resin, and about 40 parts by mass of pigment, when the resin paint forming the base coat layer 4 is taken as 100 parts by mass.

[0038] The resin coating material forming the base coat layer 4 may contain weathering agents such as ultraviolet absorbers and light stabilizers, and may also contain epoxy resins, acrylic resins, and rust inhibitors to improve corrosion resistance.

[0039] The base coat layer 4 may contain aggregate, and examples of the aggregate include acrylic resin, urea resin, nylon resin, and glass bead resin. From the viewpoint of print reproducibility and durability (corrosion resistance, etc.) of the pattern of the pattern layer 5 described below, it is preferable that the base coat layer 4 does not contain aggregate. From the viewpoints of processability, non-flammability, hiding power, corrosion resistance, etc., the thickness of the base coat layer 4 is preferably 20 μm or less.

[0040] The pattern layer 5 is a layer provided on the upper side UP of the base coat layer 4. The pattern layer 5 is a layer formed by printing a pattern such as wood grain, stone grain, sand grain, etc. As a printing method for printing the pattern layer 5, a known printing method such as gravure printing, offset printing, flexographic printing, silk screen printing, or inkjet printing can be used.

[0041] Also, known printing inks suitable for the printing method to be adopted can be used for the design layer 5. The design layer 5 contains, for example, known binder resins and known pigments. As the binder resin used for the design layer 5, it is preferable to adopt, for example, a thermosetting resin such as polyester resin, urethane resin, epoxy resin, melamine resin, alkyd resin, phenol resin, acrylic resin, etc. Also, as the pigment used for the design layer 5, for example, titanium oxide, zinc oxide (zinc white), carbon black, iron oxide, organic pigments, metallic pigments, pearl pigments, etc. can be mentioned.

[0042] The surface protective layer 6 is a layer provided on the upper side UP of the design layer 5. The surface protective layer 6 has an uneven shape on the surface of the upper side UP. FIG. 2 is a photograph showing an example of the uneven shape of the surface protective layer 6 when viewed from the upper side UP.

[0043] FIG. 3 is a cross-sectional view showing a schematic cross section of the surface protection layer 6, the cross section being parallel to the vertical direction V. As shown in FIG. The surface protective layer 6 has a core portion 6a and a plurality of ridge portions 6b protruding in a ridge shape from the surface of the upper side UP of the core portion 6a. As a result, an uneven shape is formed on the surface of the upper side UP of the surface protective layer 6.

[0044] The ridge portion 6b is formed by irradiating the upper surface UP of the surface protection layer 6 with light of a specific wavelength described below, thereby shrinking the surface of the resin (e.g., ionizing radiation curable resin) that forms the surface protection layer 6.

[0045] Here, "ridge-like" refers to a shape that rises in a long and thin shape on the upper side UP and is connected in a line when viewed from the upper side UP. The ridge-like raised ridge portions 6b may have a curved or straight shape when viewed from the upper side UP, but a curved shape is preferable from the viewpoint of the fingerprint resistance of the decorative steel sheet 10. The linear shapes of the ridge portions 6b may or may not be branched when viewed from the plan view.

[0046] The ridge portion 6b is a portion of the uneven shape provided on the surface of the upper side UP of the surface protection layer 6, ranging from the lowest point to the highest point in the up-down direction V. The core portion 6a is the portion of the surface protection layer 6 other than the ridge portion 6b.

[0047] As shown in Fig. 2, for example, each of the multiple rib portions 6b is curved, and at least some of the rib portions 6b are adjacent to each other in the width direction. Here, the width direction is the plate surface direction that is approximately perpendicular to the up-down direction V in the decorative steel sheet 10. At a position where at least some of the rib portions 6b are adjacent to each other in the width direction, the cross section of the surface protective layer 6 parallel to the width direction and the thickness direction of the surface protective layer 6 (up-down direction V) has a wave shape, such as a sine wave shape, in the portion where the uneven shape is provided, as shown in Fig. 3.

[0048] The uneven shape of the surface protective layer 6 has a ratio Rdc / t (hereinafter simply referred to as "ratio Rdc / t") of 0.1 to 0.2 of the cut level difference Rdc to the thickness t of the surface protective layer 6. The ratio Rdc / t is preferably 0.11 to 0.19.

[0049] "Cut level difference Rdc" is a surface quality parameter defined in JIS B 0601. The cut level difference Rdc indicates the cut level difference of the load curve, and expresses the steepness of the uneven shape. The ratio Rdc / t of the cut level difference Rdc to the thickness t of the surface protection layer 6 indicates the steepness of the uneven shape per unit thickness of the surface protection layer 6.

[0050] When the ratio Rdc / t is 0.1 or more and 0.2 or less, the slope of the uneven shape is relatively gentle. In this case, when the surface of the decorative steel sheet (the upper UP surface) is pressed with a finger and the finger is slid across the surface, the pressing resistance due to contact between the finger and the surface of the decorative steel sheet is small, and the contact area between the finger and the convex surface of the uneven shape gradually increases, resulting in a tactile sensation as if the surface of the decorative steel sheet is sticking to the finger. This tactile sensation can be associated with a "moist tactile sensation."

[0051] On the other hand, when the ratio Rdc / t is greater than 0.2, the slope of the uneven shape becomes steep. In this case, when a finger is pressed against the surface of the decorative steel sheet and then slid across the surface, the resistance to pressure caused by contact between the finger and the surface of the decorative steel sheet is large, and the presence of the unevenness is felt. This tactile sensation can be associated with a "rough tactile sensation."

[0052] Furthermore, when the ratio Rdc / t is smaller than 0.1, the slope of the uneven shape is very gentle. In this case, when the surface of the decorative steel sheet is pressed with a finger and slid across the surface, the pressing resistance due to contact between the finger and the surface of the decorative steel sheet is small, and the contact area between the finger and the convex surface of the uneven shape is large from the start of the pressing motion, and the increase in this contact area accompanying the pressing motion is very gentle. In this case, the surface of the decorative steel sheet feels as if it is sticking to the finger, while the very gentle slope of the uneven shape gives a smooth feel compared to the above-mentioned "moist feel", and overall the impression of a smooth feel is stronger. This feel can be associated with a "smooth feel".

[0053] The thickness t of the surface protective layer 6 is 5 μm or more. In addition, the thickness t of the surface protective layer 6 is preferably 18 μm or less. By making the thickness t of the surface protective layer 6 5 μm or more, the layers provided on the lower side LO of the surface protective layer 6 can be protected from ultraviolet rays, acid rain, salt, etc., and the weather resistance of the decorative steel sheet 10 can be improved.

[0054] Furthermore, there is a tendency for the ratio Rdc / t to increase as the thickness of the surface protective layer 6 increases. Therefore, if the thickness of the surface protective layer 6 is too small or too large, it becomes difficult to achieve a "moist tactile feel."

[0055] Here, the thickness t of the surface protection layer 6 is the thickness of a layer that has the same apparent area and volume as the surface protection layer 6 and has a flat surface (upper UP surface). The thickness t of the surface protection layer 6 can be determined, for example, by the following method. First, a cross section that is parallel to the thickness t direction (vertical direction V) of the surface protection layer 6 and perpendicular to the length direction of the ridge-like portion 6b is imaged to obtain a cross-sectional image. Here, the length direction of the ridge-like portion 6b is the direction in which the ridge shape of the ridge-like portion 6b extends.

[0056] Next, from this cross-sectional image, the dimension of the surface protective layer 6 in the width direction of the ridge portion 6b and the cross-sectional area of ​​the surface protective layer 6 are obtained. The thickness t of the surface protective layer 6 is a value obtained by dividing the cross-sectional area by the above-mentioned dimension. Note that, when the resin forming the surface protective layer 6 does not contain a solvent, the thickness of the coating film made of the resin forming the surface protective layer 6 is equal to the thickness t of the surface protective layer 6.

[0057] Hereinafter, the resin forming the surface protective layer 6 may be referred to as a coating liquid for surface protective layer. The surface protective layer 6 is formed by curing a coating liquid for surface protective layer that contains a curable resin such as an ionizing radiation curable resin.

[0058] The coating liquid for the surface protective layer may be an ionizing radiation curable resin such as a (meth)acrylic resin, a silicone resin, a polyester resin, a urethane resin, an amide resin, or an epoxy resin. The ionizing radiation curable resin used in the coating liquid for the surface protective layer may be either an aqueous resin or a non-aqueous (organic solvent) resin. In addition, it is preferable to use a transparent or semi-transparent material for the surface protective layer 6 so that the pattern of the pattern layer 5 can be seen through.

[0059] Here, "ionizing radiation" refers to a charged particle beam such as an electron beam. Ionizing radiation curable resins are cured by irradiation with ionizing radiation. Ionizing radiation curable resins can also be cured by ultraviolet light irradiation. The ionizing radiation curable resins used here are cured by irradiation with light having a wavelength of 200 nm or less, and have a large absorption coefficient for this light.

[0060] The coating liquid for forming the surface protective layer 6 may contain additives such as a solvent, an antibacterial agent, or an antifungal agent. The coating liquid for forming the surface protective layer may also contain an ultraviolet absorber or a light stabilizer. As the ultraviolet absorber, for example, a benzotriazole-based, benzoate-based, benzophenone-based, or triazine-based agent may be used. As the light stabilizer, for example, a hindered amine-based agent may be used.

[0061] Moreover, the surface protective layer 6 preferably contains particles having an average particle size of 3 μm or more. Examples of the particles contained in the surface protective layer 6 include particles made of organic materials such as polyethylene (PE) wax, polypropylene (PP) wax, and resin beads, and particles made of inorganic materials such as silica, glass, alumina, titania, zirconia, calcium carbonate, and barium sulfate.

[0062] The average particle size (D50) of the particles contained in the surface protective layer 6 is preferably 3 μm or more and 11 μm or less, and more preferably 4 μm or more and 10 μm or less.

[0063] By including particles in the surface protective layer 6, wrinkles can be more uniformly generated on the coating surface in the first irradiation step described below. As the average particle size (D50) of the particles increases, the value of the ratio Rdc / t tends to decrease. For this reason, if the average particle size (D50) is too small or too large, it becomes difficult to achieve a "moist tactile feel." In addition, when particles with a large particle size are used, the particles are likely to fall off from the surface protective layer 6, and it may become difficult to achieve high scratch resistance. If the particle size is small, the effect of generating wrinkles uniformly is small.

[0064] Here, the "average particle size (D50)" is the median size (D50) measured by a laser diffraction / scattering type particle size distribution analyzer. When the coating liquid for the surface protective layer contains particles, the surface protective layer 6 obtained from this coating liquid also contains particles. The average particle size of the particles contained in the surface protective layer 6 can be determined by observing the cross section of the layer and averaging the particle sizes of a plurality of particles. The value obtained in this manner is substantially the same as the median size (D50) measured by a laser diffraction / scattering type particle size distribution analyzer.

[0065] The 60-degree reflected gloss of the surface protective layer 6 is preferably 10.0 or less. Here, the reflected gloss in this embodiment refers to the specular gloss defined in JIS Z 8741. The 60-degree reflected gloss refers to the 60-degree specular gloss in the above-mentioned JIS standard, and refers to the gloss of reflected light of light with an incident angle α of 60 degrees as shown in FIG. 3. By setting the 60-degree reflected gloss to 10.0 or less, the decorative steel sheet 10 can have an excellent low-gloss design. The gloss of reflected light can be measured by a measuring instrument such as a surface gloss meter.

[0066] A known printing method such as gravure printing, offset printing, flexographic printing, silk screen printing, or inkjet printing can be used as a method for forming the surface protective layer 6. The surface protective layer 6 may also be formed using a known coating device.

[0067] Next, an example of a method for manufacturing the decorative steel sheet 10 will be described. 4 is a flow chart showing an example of a manufacturing method for manufacturing the decorative steel plate 10 by a decorative steel plate manufacturing system. Here, the decorative steel plate manufacturing system is a system that executes the manufacturing of the decorative steel plate 10 according to this embodiment.

[0068] First, the decorative steel sheet manufacturing system performs step S1 (chemical conversion treatment step). In step S1, chemical conversion treatment is performed on the surfaces of the upper side UP and the lower side LO of the steel sheet layer 1a to form a first chemical conversion treatment layer 1b and a second chemical conversion treatment layer 1c, thereby forming a plated steel sheet layer 1.

[0069] Next, the decorative steel sheet manufacturing system performs step S2 (primer layer / rear coat layer forming process). In step S2, a resin paint for forming a rear coat layer 2 is applied to the surface of the lower side LO of the plated steel sheet layer 1 formed in step S1. In addition, a resin paint for forming a primer layer 3 is applied to the surface of the upper side UP of the plated steel sheet layer 1.

[0070] The upper UP and lower LO surfaces of the plated steel sheet layer 1, to which the resin paint forming the back surface coating layer 2 and the resin paint forming the primer layer 3 have been applied, are baked and dried to form the back surface coating layer 2 and the primer layer 3. The baking and drying temperature is, for example, 200° C. or higher.

[0071] Next, the decorative steel plate manufacturing system performs step S3 (base coat layer forming process). In step S3, a resin paint for forming a base coat layer 4 is applied to the upper surface UP of the primer layer 3 formed in step S2, and baked and dried to form the base coat layer 4. Here, the temperature for baking and drying is, for example, 200°C or higher.

[0072] Next, the decorative steel plate manufacturing system performs step S4 (pattern printing step). In step S4, an arbitrary pattern is printed on the upper surface UP of the base coat layer 4 to form a pattern layer 5.

[0073] Next, the decorative steel sheet manufacturing system performs step S5 (protective layer application step). In step S5, a resin (surface protective layer coating liquid) that forms the surface protective layer 6 is applied to the upper UP surface of the design layer 5. Here, the surface protective layer coating liquid is an ionizing radiation curable resin.

[0074] Next, the decorative steel sheet manufacturing system performs step S6 (first irradiation step). In step S6, the upper surface UP (front surface) of the coating liquid for surface protection layer applied in step S6 is irradiated with excimer VUV light having a wavelength of 172 nm. By irradiating with excimer VUV light having a wavelength of 200 nm or less, the surface of the ionizing radiation curable resin shrinks, and ridge-like portions 6b in the surface protection layer 6 are formed.

[0075] Here, the ionizing radiation curable resin contained in the coating liquid for surface protective layer has a large absorption coefficient for excimer VUV light. Therefore, the excimer VUV light incident on the coating film of the coating liquid for surface protective layer can only reach a position that is several tens to several hundreds of nm away from the outermost surface. Therefore, in step S6, the crosslinking reaction proceeds in the surface region of the coating film of the coating liquid for surface protective layer, forming an extremely thin cured film. Meanwhile, in other regions, the crosslinking reaction does not proceed and the coating liquid for surface protective layer remains uncured.

[0076] Next, the decorative steel plate manufacturing system carries out step S7 (second irradiation step). In step S7, ionizing radiation is irradiated onto the surface of the coating liquid for surface protection layer on which the ribbed portions 6b have been formed in step S6. By irradiating the ionizing radiation curable resin on which the ribbed portions 6b have been formed by the excimer VUV light with ionizing radiation, the entire ionizing radiation curable resin is cured, and a surface protection layer 6 having an uneven shape with the core portions 6a and the ribbed portions 6b is formed is formed. With the surface protection layer 6 formed, the manufacturing process for the decorative steel plate 10 is completed.

[0077] According to the decorative steel sheet 10 and the manufacturing method of the decorative steel sheet 10 of this embodiment, the decorative steel sheet 10 has a surface protective layer 6 having an uneven shape on the upper side UP and a thickness of 5 μm or more. Moreover, the uneven shape of the surface protective layer 6 has a ratio Rdc / t of the cut level difference Rdc to the thickness t of the surface protective layer 6 of 0.1 or more and 0.2 or less.

[0078] In the uneven shape of the surface protection layer 6, the ratio Rdc / t of the cut level difference Rdc to the thickness t of the surface protection layer 6 is 0.1 or more and 0.2 or less, so that the decorative steel plate 10 gives the user a moist feel when the user presses the surface of the surface protection layer 6 with the skin and slides his / her finger over the surface, and has an excellent feel to the touch. As a result, it is possible to provide a decorative steel sheet 10 having an excellent feel and a manufacturing method for the decorative steel sheet 10.

[0079] In addition, the decorative steel plate 10 can achieve an excellent feel without using aggregates or embossed plates, so that it is possible to suppress the deterioration of the printing reproducibility of the pattern layer 5 caused by aggregates and the deterioration of productivity caused by using embossed plates. In addition, the decorative steel plate 10 has excellent weather resistance because the thickness of the surface protective layer 6 is 5 μm or more.

[0080] Although one embodiment of the present invention has been described in detail above with reference to the drawings, the specific configuration is not limited to this embodiment, and design modifications and the like within the scope of the present invention are also included. In addition, the components shown in the above-mentioned embodiment and the modified examples shown below can be appropriately combined to form a configuration.

[0081] (Variation 1) In the above embodiment, the decorative steel sheet 10 includes the primer layer 3, but the aspect of the decorative steel sheet 10 is not limited to this. The decorative steel sheet does not necessarily need to include the primer layer 3. The decorative steel sheet 10 has a primer layer 3, which can improve adhesion between the plated steel sheet layer 1 and the base coat layer 4. If the plated steel sheet layer 1 and the base coat layer 4 can have sufficient adhesion without improving the adhesion with the primer layer 3, the decorative steel sheet does not need to have the primer layer 3.

[0082] The present invention will be described in detail below with reference to examples, but the present invention is not limited to the following examples.

[0083] Example 1 (Chemical conversion treatment process S1) A hot-dip galvanized steel sheet having a thickness of 0.4 mm conforming to JIS G 3302 was prepared as the steel sheet layer 1a, and a chemical conversion treatment was applied to the steel sheet layer 1a to form a first chemical conversion treatment layer 1b and a second chemical conversion treatment layer 1c, thereby forming a plated steel sheet layer 1 which is an alloyed galvanized steel sheet.

[0084] (Primer layer / backside coat layer formation process S2) As the resin paint for forming the back surface coating layer 2, a resin paint containing polyester resin and epoxy resin as main components was applied to the surface of the lower side LO of the plated steel sheet layer 1.

[0085] In addition, a resin paint containing about 57 parts by mass of polyester resin, about 1 part by mass of an organic additive, and about 42 parts by mass of a pigment as main ingredients was applied to the upper UP surface of the plated steel sheet layer 1 as the resin paint for forming the primer layer 3. The resin paint for forming the primer layer 3 was applied so that the thickness of the primer layer 3 became 1.0 μm or more.

[0086] After applying a resin paint for forming the back coat layer 2 and a resin paint for forming the primer layer 3, the coating was baked and dried at 200° C. or higher to form the back coat layer 2 and the primer layer 3.

[0087] (Base coat layer forming process S3) The resin paint for forming the base coat layer 4 was made of approximately 45 parts by mass of polyester resin, approximately 15 parts by mass of melamine resin, and approximately 40 parts by mass of pigment as main ingredients, and was applied to the upper UP surface of the primer layer 3 to a thickness of approximately 13 μm, and was baked and dried at 200° C. or higher to form the base coat layer 4. No aggregate was added to the base coat layer 4.

[0088] (Pattern printing process S4) A pattern was printed on the upper surface UP of the base coat layer 4 by gravure offset printing to a thickness of about several μm to form a design layer 5.

[0089] (Protective layer coating process S5) A coating liquid for forming a surface protective layer 6 was applied to the upper surface UP of the design layer 5. The layer thickness of the coating liquid for the surface protective layer was 10.8 μm. The coating liquid used for the surface protective layer was a coating liquid obtained by blending the following ionizing radiation curable resin with the following particles and photopolymerization initiator. ·Ionizing radiation curable resin Type: Trimethylolpropane EO modified triacrylate (EO 15 moles added) Product name: SR9035 (Sartomer) Blend: 100 parts by mass ·particle Product name: Silica 250N (manufactured by Fuji Silysia Chemical) Particle size: 6μm Blend: 5 parts by mass Photopolymerization initiator Product name: Omnirad184 (IGM Resins) Blend: 3 parts by mass

[0090] (1st irradiation step S6) The upper surface UP of the coating liquid for the surface protective layer applied in the protective layer application step S5 was irradiated with excimer VUV light using a Xe excimer lamp to shrink the surface of the coating liquid for the surface protective layer and generate wrinkles. At this time, the integrated light amount of ultraviolet light with a wavelength of 172 nm was 30 mJ / cm in a nitrogen gas atmosphere with an oxygen concentration of 100 ppm under atmospheric pressure. 2 The irradiation was performed so that

[0091] (Second irradiation step S7) The coating liquid for the surface protective layer that was shrunk by the excimer VUV light in the first irradiation step S6 was irradiated with 200 mJ / cm using a high-pressure mercury lamp. 2 The coating liquid for surface protective layer was entirely cured to form the surface protective layer 6. In this way, the decorative steel sheet 10 of Example 1 was obtained.

[0092] Example 2 A decorative steel sheet 10 of Example 2 was obtained in the same manner as in Example 1, except that the thickness of the coating liquid for the surface protective layer was set to 14.0 μm.

[0093] Comparative Example 1 A decorative steel sheet of Comparative Example 1 was obtained in the same manner as in Example 1, except that the thickness of the coating liquid for surface protection layer was set to 5.0 μm.

[0094] Comparative Example 2 A decorative steel sheet of Comparative Example 2 was obtained in the same manner as in Example 1, except that the thickness of the coating liquid for surface protection layer was set to 7.1 μm.

[0095] Comparative Example 3 A decorative steel sheet of Comparative Example 3 was obtained in the same manner as in Example 1, except that the thickness of the coating liquid for surface protection layer was set to 3.0 μm.

[0096] Comparative Example 4 A decorative steel sheet of Comparative Example 4 was obtained in the same manner as in Example 1, except that the thickness of the coating liquid for surface protection layer was set to 21.1 μm.

[0097] Comparative Example 5 A decorative steel sheet of Comparative Example 5 was obtained in the same manner as in Example 1, except that the thickness of the coating liquid for surface protective layer was set to 17.0 μm.

[0098] Comparative Example 6 A decorative steel sheet of Comparative Example 6 was obtained in the same manner as in Example 1, except that the thickness of the coating liquid for surface protection layer was set to 2.0 μm.

[0099] Comparative Example 7 A decorative steel sheet of Comparative Example 7 was obtained in the same manner as in Example 1, except that the thickness of the coating liquid for surface protection layer was set to 1.4 μm.

[0100] Comparative Example 8 A decorative steel sheet of Comparative Example 8 was obtained in the same manner as in Example 1, except that the thickness of the coating liquid for surface protection layer was set to a layer thickness of 0.8 μm.

[0101] Comparative Example 9 A decorative steel sheet of Comparative Example 9 was obtained in the same manner as in Example 1, except that an acrylic resin containing aggregate was used as the surface protective layer, and the thickness of the surface protective layer was set to about 10 μm. The composition of the aggregate added to the surface protective layer was 7.0% 5 μm organic resin beads and 0.5% 4 μm silica.

[0102] Comparative Example 10 A decorative steel sheet of Comparative Example 10 was obtained in the same manner as in Example 1, except that an acrylic resin with added aggregate was used as the surface protective layer, and the thickness of the surface protective layer was set to about 10 μm. The composition of the aggregate added to the surface protective layer was 4.4% 15 μm acrylic beads, 6.9% 5 μm organic resin beads, and 1.9% 4 μm silica.

[0103] Comparative Example 11 A decorative steel sheet of Comparative Example 11 was obtained in the same manner as in Example 1, except that an acrylic resin with added aggregate was used as the surface protective layer, and the thickness of the surface protective layer was set to about 10 μm. The composition of the aggregate added to the surface protective layer was 8.8% 15 μm acrylic beads, 14.1% 5 μm organic resin beads, and 1.6% 4 μm silica.

[0104] (Experiment 1) For the decorative steel sheets of Example 1-2 and Comparative Example 1-11, "reflected gloss (20 degrees, 60 degrees, 85 degrees)" and "ratio Rdc / t of cut level difference Rdc to thickness t of surface protective layer" were measured. Here, the 20-degree reflected gloss and 85-degree reflected gloss are specular gloss values ​​defined in JIS Z 8741, similar to the 60-degree reflected gloss, and respectively indicate the gloss of reflected light for light with an incident angle α of 20 degrees or 85 degrees as shown in FIG. 3.

[0105] (Experiment 2) A tactile evaluation test was carried out on the decorative steel sheets of Example 1-2 and Comparative Example 1-11. In the tactile evaluation test, first, advance preparation was carried out to ensure that the evaluation criteria were consistent between evaluators. In advance preparation, three standard test pieces with different surface properties were prepared. Next, five blindfolded evaluators pressed and slid their fingers over the surface of the standard test pieces, and classified the tactile sensation into the following three groups. Group 1: Almost no resistance was felt when pushing, but the surface of the decorative steel sheet felt as if it was sticking to the fingers, and it also felt smooth to the touch. Overall, the impression of a smooth texture was strong. In other words, a "smooth texture" was obtained. Group 2: Almost no resistance was felt when pushing, but the surface of the decorative steel sheet felt as if it was sticking to the fingers. However, there was no impression of a smooth feel. In other words, a "moist feel" was felt. Group 3: They felt resistance to pressure and also felt the presence of unevenness. In other words, they felt a "rough texture."

[0106] Next, five blindfolded evaluators pressed and slid their fingers over the surfaces of the decorative steel sheets of Examples 1-2 and Comparative Examples 1-11, and evaluated the feel of the sheets by focusing on the difference from the feel of the standard test pieces classified into Group 2. The evaluation criteria were three-level. ◯: The feel is close to that of the standard test piece classified as Group 2. △: The texture is different from that of the standard test piece classified as group 2, but the smoothness is similar. ×: The feel is clearly different from that of the standard test piece classified as group 2.

[0107] (Experimental Results) The results of Experiment 1 and Experiment 2 are shown in Table 1. As shown in Table 1, the decorative steel sheet 10 of Example 1-2, in which the uneven shape was realized by the ridge-like shape formed on the surface protective layer 6, the thickness of the surface protective layer 6 was 5 μm or more, and the ratio Rdc / t was 0.1 or more and 0.2 or less, had a feel similar to that of the standard test piece classified in the second group. In addition, the decorative steel sheet of Comparative Example 9-10, which did not have a ridge-like shape and had a ratio Rdc / t of 0.1 or more and 0.2 or less, had a feel similar to that of the standard test piece classified in the second group. That is, Examples 1-2 and Comparative Examples 9-10 had a "moist feel".

[0108] Furthermore, even though the decorative steel sheet had a concave-convex shape formed in the surface protective layer, Comparative Example 1-8, in which the ratio Rdc / t was greater than 0.2, had a different feel to the touch from the standard test pieces classified in Group 2.

[0109] [Table 1] [Explanation of symbols]

[0110] 10 Decorative steel plate 1. Plated steel layer 1 1a steel plate layer 1b First chemical conversion coating layer (chemical conversion coating layer) 1c Second chemical conversion coating layer (chemical conversion coating layer) 2 Backside coating layer 3 Primer layer 4 Basecoat Layer 5. Picture layer 6 Surface protective layer 6a Core section 6b Ridged part V vertical direction UP upper side LO Lower

Claims

1. A plated steel layer; A base coat layer provided on the upper side of the plated steel sheet layer; A design layer provided on the upper side of the base coat layer; A surface protective layer having an uneven shape on the upper surface thereof and a thickness of 5 μm or more, the surface protective layer being provided on the upper side of the design layer; Equipped with The uneven shape of the surface protective layer has a ratio of a cut level difference Rdc to the thickness of the surface protective layer of 0.1 or more and 0.2 or less. Decorative steel plate.

2. The plated steel sheet layer has a steel sheet layer and a chemical conversion treatment layer provided on the upper side of the steel sheet layer. The decorative steel sheet according to claim 1 .

3. Further comprising a primer layer provided on the upper side of the plated steel sheet layer. The decorative steel sheet according to claim 1 .

4. The surface protective layer is The thickness is 18 μm or less, Contains particles with an average particle size of 3 μm or more and 11 μm or less; The decorative steel sheet according to claim 1 .

5. The surface protective layer has a 60-degree reflected gloss of 10.0 or less. The decorative steel sheet according to claim 1 .

6. The uneven shape of the surface protective layer has a plurality of ridge-like portions that are raised in a ridge-like shape and adjacent to each other in a width direction, The plurality of ridge portions adjacent to each other in the width direction have a sine wave shape in a cross section parallel to the up-down direction. The decorative steel sheet according to claim 1 .

7. The surface protective layer contains an ionizing radiation curable resin. The decorative steel sheet according to claim 1 .

8. The plated steel sheet layer includes a zinc-plated steel sheet or an aluminum-zinc alloy-plated steel sheet; The decorative steel sheet according to any one of claims 1 to 7.

9. a protective layer application step of forming a surface protective layer having a thickness of 5 μm or more on an upper side of the plated steel sheet layer; a first irradiation step of irradiating a surface of the surface protective layer with light having a wavelength of 200 nm or less to form an uneven shape so that a ratio of a cut level difference Rdc to the thickness of the surface protective layer is 0.1 to 0.2; Equipped with A manufacturing method for decorative steel sheets.

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