Title of Invention	SURFACE -TREATED STEEL SHEET , METHOD FOR PRODCUING THE SAME, AND RESIN COATED STEEL SHEET
Abstract	It is an object to provide a surface-treated steel sheet which contains no Cr, which is excellent in wet resin adhesion, and which can be used as an alternative to a conventional tin-free steel sheet and to provide a resin- coated steel sheet produced by coating the surface-treated steel sheet with resin. A surface-treated steel sheet including an adhesive layer which is disposed on at least one surface of the steel sheet and which contains Ti and at least one selected from the group consisting of Co, Fe, Ni, V, Cu, Mn, and Zn, the ratio of the total amount of Co, Fe, Ni, V, Cu, Mn, and Zn to the amount of Ti contained therein being 0.01 to ten on a mass basis, and a method for producing the surface-treated steel sheet. A surface-treated steel sheet including an adhesive layer which is disposed on at least one surface of the steel sheet, which has a thickness of 20 to 800 nm, which contains Ti, and which has bumps arranged with a line density of one or more per μm. The thickness of the adhesive layer is defined as the maximum height H from the lower surface of the adhesive layer to the bumps in a cross-sectional profile of the layer observed with a transmission electron microscope (TEM) . The line density of the bumps is defined as the number of the bumps per unit length, the number thereof being determined on the assumption that one of the bumps is

Title of Invention

SURFACE -TREATED STEEL SHEET , METHOD FOR PRODCUING THE SAME, AND RESIN COATED STEEL SHEET

Abstract

It is an object to provide a surface-treated steel sheet which contains no Cr, which is excellent in wet resin adhesion, and which can be used as an alternative to a conventional tin-free steel sheet and to provide a resin- coated steel sheet produced by coating the surface-treated steel sheet with resin. A surface-treated steel sheet including an adhesive layer which is disposed on at least one surface of the steel sheet and which contains Ti and at least one selected from the group consisting of Co, Fe, Ni, V, Cu, Mn, and Zn, the ratio of the total amount of Co, Fe, Ni, V, Cu, Mn, and Zn to the amount of Ti contained therein being 0.01 to ten on a mass basis, and a method for producing the surface-treated steel sheet. A surface-treated steel sheet including an adhesive layer which is disposed on at least one surface of the steel sheet, which has a thickness of 20 to 800 nm, which contains Ti, and which has bumps arranged with a line density of one or more per μm. The thickness of the adhesive layer is defined as the maximum height H from the lower surface of the adhesive layer to the bumps in a cross-sectional profile of the layer observed with a transmission electron microscope (TEM) . The line density of the bumps is defined as the number of the bumps per unit length, the number thereof being determined on the assumption that one of the bumps is

Full Text	DESCRIPTION SURFACE-TREATED STEEL SHEET, METHOD FOR PRODUCING THE SAME, AND RESIN-COATED STEEL SHEET Technical Field The present invention relates to surface-treated steel sheets which are used principally for containers such as cans after being coated with resin in such a manner that resin films or the like are laminated on the surface-treated steel sheets or resin- containing paints are applied onto the surface-treated steel sheets. The present invention particularly relates to a surface- treated steel sheet having high adhesion (hereinafter referred to as wet resin adhesion) to resin applied thereto in a high- temperature humid environment, a method for producing the surface- treated steel sheet, and a resin-coated steel sheet produced by coating the surface-treated steel sheet with resin. The present invention further relates to a surface-treated steel sheet that exhibits high corrosion resistance even if resin applied thereto is peeled therefrom, a method for producing the surface-treated steel sheet, and a resin-coated steel sheet produced by coating the surface-treated steel sheet with resin. Background Art Tin-plated steel sheets and electrolytically chromated steel sheets referred to as tin-free steel sheets are used for various metal cans such as beverage cans, food cans, pail cans, and 18- litter cans. In particular, the tin-free steel sheets are produced by electrolyzing steel sheets in a plating bath containing hexavalent chromium and have the advantage of having excellent wet resin adhesion to resin such as paint. In recent years, the use of hexavalent chromium has tended to be restricted worldwide in response to growing environmental awareness. Alternatives to the tin-free steel sheets, which are produced using such a plating bath containing hexavalent chromium, have been needed. For example, Japanese Unexamined Patent Application Publication No. 2004-285380 discloses a steel sheet, electrolyzed in a tungstic acid solution, for containers. Japanese Unexamined Patent Application Publication No. 2001-220685 discloses a surface-treated steel sheet, coated with a phosphonate layer, for containers. Japanese Unexamined Patent Application Publication No. 2002-355921 discloses a steel sheet, coated with a surface treatment layer containing one or both of Sn and Ni, for containers, the surface treatment layer being overlaid with a resin layer which contains one or both of tannic acid and acetic acid and Ti, Zn, or one or more of compounds thereof and which has a phenol structure. Japanese Unexamined Patent Application Publication No. 2006-009046 discloses a surface-treated metal material having an organic surface treatment layer and an inorganic surface treatment layer which contains no phosphate ion but principally contains T, 0, and/or F. Various types of metal cans have been conventionally manufactured in such a manner that metal sheets such as tin-free steel sheets are painted and then formed into can bodies. In recent years, the following method has been widely used to reduce the amount of industrial waste: a method in which a resin-coated metal sheet that is not painted but is coated with resin such as a resin film is formed into a can body. For the resin-coated metal sheet, the resin needs to strongly adhere to the metal sheet. In particular, resin-coated metal sheets used for beverage or food cans need to have high wet resin adhesion such that no resin is peeled therefrom even in high-temperature humid environments, because the beverage or food cans are subjected to retort sterilization steps in some cases after contents are packed in the beverage or food cans. Furthermore, the resin-coated metal sheets need to have high corrosion resistance such that the cans are prevented from being perforated by corrosion due to the contents of the cans even if resin is partly peeled from the cans by scratching. The following sheets and material have insufficient wet resin adhesion when being used in a retort atmosphere: the steel sheet electrolyzed in the tungstic acid solution as disclosed in Japanese Unexamined Patent Application Publication No. 2004-285380, the surface-treated steel sheet coated with the phosphonate layer as disclosed in Japanese Unexamined Patent Application Publication No. 2001-220685, the steel sheet having the resin layer having the phenol structure as disclosed in Japanese Unexamined Patent Application Publication No. 2002-355921, and the surface-treated metal material having the organic surface treatment layer and the inorganic surface treatment layer principally containing T, 0, and/or F as disclosed in Japanese Unexamined Patent Application Publication No. 2006-009046. It is an object of the present invention to provide a surface- treated steel sheet which contains no Cr, which has excellent wet resin adhesion, and which can be used as an alternative to a tin- free steel sheet; a method for producing the surface-treated steel sheet; and a resin-coated steel sheet produced by coating the surface-treated steel sheet with resin. Disclosure of Invention The scope of the present invention is as described below. 1. A surface-treated steel sheet includes an adhesive layer which is disposed on at least one surface of the steel sheet and which contains Ti and at least one selected from the group consisting of Co, Fe, Ni, V, Cu, Mn, and Zn. The ratio of the total amount of Co, Fe, Ni, V, Cu, Mn, and Zn to the amount of Ti contained therein is 0.01 to ten on a mass basis. 2. In the surface-treated steel sheet specified in Item 1, the adhesive layer has a thickness of 20 to 800 nm and also has bumps arranged with a line density of one or more per µm, the thickness of the adhesive layer is defined as the maximum height H from the lower surface of the adhesive layer to the bumps in a cross- sectional profile of the layer observed with a transmission electron microscope (TEM), and the line density of the bumps is defined as the number of the bumps per unit length. The number thereof is determined on the assumption that one of the bumps is present when one or more intersections of an upper-level horizontal line and a profile curve are present between two intersections of a lower-level horizontal line and the profile curve. The upper- and lower-level horizontal lines are ±10 nm apart from a center line located at a position given by the formula (H + L) / 2, where L represents the minimum height from the lower surface of the adhesive layer to the bottom of a recessed portion. 3. In the surface-treated steel sheet specified in Item 1, the adhesive layer has a thickness of 20 to 800 nm and also has bumps arranged with an area density of 16 or more per µm2 and the area density of the bumps of the adhesive layer is defined as the number of the bumps that are 0.005 µm higher than an average line of the bumps and recessed portions. The average line is determined in such a manner that a SEM image of the layer observed with a scanning electron microscope (SEM) is three-dimensionally analyzed and filtered at a cut-off wavelength of 1.0 µm. 4. In the surface-treated steel sheet specified in Item 3, the ratio (Rq / Ra) of root-mean-square roughness (Rq) to arithmetic average roughness (Ra) is 1.3 or less. The root-mean-square roughness and the arithmetic average roughness are specified in JIS B 0601: 2201 and determined in such a manner that a cross- sectional curve is derived from three-dimensional data obtained with a SEM and then filtered at a cut-off wavelength of 1.0 µm. 5. In the surface-treated steel sheet specified in Item 3 or 4, skewness (Rsk) is 0.6 or less or kurtosis (Rku) is four or less. The skewness and the kurtosis are specified in JIS B 0601: 2201 and determined in such a manner that a cross-sectional curve is derived from three-dimensional data obtained with a SEM and then filtered at a cut-off wavelength of 1.0 µm. 6. A surface-treated steel sheet includes an adhesive layer which is disposed on at least one surface of the steel sheet, which has a thickness of 20 to 800 nm, which contains Ti, and which has bumps arranged with a line density of one or more per µm. The thickness of the adhesive layer is defined as the maximum height H from the lower surface of the adhesive layer to the bumps in a cross-sectional profile of the layer observed with a transmission electron microscope (TEM). The line density of the bumps is defined as the number of the bumps per unit length. The number thereof is determined on the assumption that one of the bumps is present when one or more intersections of an upper-level horizontal line and a profile curve are present between two intersections of a lower-level horizontal line and the profile curve. The upper- and lower-level horizontal lines are ±10 nm apart from a center line located at a position given by the formula (H + L) / 2, where L represents the minimum height from the lower surface of the adhesive layer to the bottom of a recessed portion. 7. A surface-treated steel sheet includes an adhesive layer which is disposed on at least one surface of the steel sheet, which has a thickness of 20 to 800 nm, which contains Ti, and which has bumps arranged with an area density of 16 or more per urn2. The area density of the bumps of the adhesive layer is defined as the number of the bumps that are 0.005 µm higher than an average line of the bumps and recessed portions. The average line is determined in such a manner that a SEM image of the layer observed with a scanning electron microscope (SEM) is three-dimensionally analyzed and filtered at a cut-off wavelength of 1.0 \|im. 8. In the surface-treated steel sheet specified in Item 7, the ratio (Rq / Ra) of root-mean-square roughness (Rq) to arithmetic average roughness (Ra) is 1.3 or less. The root-mean-square roughness and the arithmetic average roughness are specified in JIS B 0601: 2201 and determined in such a manner that a cross- sectional curve is derived from three-dimensional data obtained with a SEM and then filtered at a cut-off wavelength of 1.0 µm. 9. In the surface-treated steel sheet specified in Item 7 or 8, skewness (Rsk) is 0.6 or less or kurtosis (Rku) is four or less. The skewness and the kurtosis are specified in JIS B 0601: 2201 and determined in such a manner that a cross-sectional curve is derived from three-dimensional data obtained with a SEM and then filtered at a cut-off wavelength of 1.0 µm. 10. In the surface-treated steel sheet specified in any one of Items 1 to 9, the amount of Ti in the adhesive layer is 3 to 200 mg/m2 per one surface. 11. The surface-treated steel sheet specified in any one of Items 1 to 10 further includes a corrosion-resistant layer which is disposed on at least one surface of the steel sheet; which includes at least one selected from the group consisting of a Ni layer, a Sn layer, a Fe-Ni alloy layer, a Fe-Sn alloy layer, and a Fe-Ni-Sn alloy layer; and which is disposed under the adhesive layer. 12. The surface-treated steel sheet specified in any one of Items 1 to 11 is coated with resin. 13. A method for producing a surface-treated steel sheet includes forming a corrosion-resistant layer, including at least one selected from the group consisting of a Ni layer, a Sn layer, a Fe-Ni alloy layer, a Fe-Sn alloy layer, and a Fe-Ni-Sn alloy layer, on at least one surface of a steel sheet and also includes forming an adhesive layer in such a manner that the resulting steel sheet is cathodically electrolyzed in an aqueous solution containing ions of Ti and ions of at least one selected from the group consisting of Co, Fe, Ni, V, Cu, Mn, and Zn. 14. In the surface-treated steel sheet-producing method specified in Item 13, the content of Ti in the aqueous solution is 0.008 to 0.07 mol/1 and the molar ratio of at least one selected from the group consisting of Co, Fe, Ni, V, Cu, Mn, and Zn to Ti in the aqueous solution is 0.01 to 10. 15. In the surface-treated steel sheet-producing method specified in Item 13 or 14, the amount of Ti in the adhesive layer is 3 to 200 mg/m2 per one surface. Brief Description of Drawings Figs. 1A and 1B are schematic sectional views of adhesive layers included in surface-treated steel sheets according to the present invention. Figs. 2A and 2B are schematic sectional views of adhesive layers included in surface-treated steel sheets of comparative examples. Figs. 3A and 3B are images illustrating the TEM observation results of a cross-sectional surface of an adhesive layer of an example of the present invention and a cross-sectional surface of a layer of a comparative example. Fig. 4 is a schematic view illustrating the thickness of an adhesive layer included in a surface-treated steel sheet according to the present invention and the line density of bumps of the adhesive layer. Figs. 5A and 5B are images illustrating the SEM observation results of an adhesive layer of an example of the present invention and a layer of a comparative example. Figs. 6A, 6B, and 6C are illustrations showing a 180° peeling test. [Reference Numerals] 1 steel sheet 2 film 3 notched portion of steel sheet 4 weight 5 peeled length Best Modes for Carrying Out the Invention The inventors have conducted intensive research on surface- treated steel sheets which contain no Cr, which have excellent wet resin adhesion, and which can be used as alternatives to tin-free steel sheets and have then obtained findings below. (1) Extremely excellent wet resin adhesion can be achieved by forming an adhesive layer containing Ti and an element such as Co, Fe, Ni, V, Cu, Mn, or Zn on a steel sheet. (2) In order to achieve extremely excellent wet resin adhesion, an adhesive layer having a large number of fine bumps arranged uniformly is preferably formed. The present invention has been made on the basis of these findings. The contents of the present invention will now be described in detail. (1) Surface-treated steel sheet A surface-treated steel sheet according to the present invention includes an adhesive layer which is disposed on at least one surface of the surface-treated steel sheet and which contains Ti and at least one selected from the group consisting of Co, Fe, Ni, V, Cu, Mn, and Zn. An ordinary steel sheet, such as a low-carbon steel sheet or an ultra-low-carbon steel sheet, for cans can be used as a raw steel sheet. A steel sheet coated with an adhesive layer containing Ti or an adhesive layer which contains Ti and at least one selected from the group consisting of Co, Fe, Ni, V, Cu, Mn, and Zn has excellent wet resin adhesion. The reason for this is unclear at present and is probably that a strong intermolecular force is present between resin and a layer which is composed of an oxide of Ti and which has high molecular weight or that the above metal element is taken in the layer containing Ti and therefore the layer has surface irregularities which are densely and uniformly distributed. The ratio of the total amount of Co, Fe, Ni, V, Cu, Mn, and Zn to the amount of Ti in the adhesive layer needs to be 0.01 to ten on a mass basis. This allows the adhesive layer to have surface irregularities which are densely and uniformly distributed, thereby achieving excellent wet resin adhesion. The mass ratio thereof is preferably 0.1 to two. The content of the metal elements in the adhesive layer can be determined by energy- dispersive x-ray analysis (EDX) or electron energy loss spectroscopy (EELS) in TEM observation below. In view of an increase in wet resin adhesion, the adhesive layer preferably further contains 0. The presence of 0 probably allows the adhesive layer to be composed of an oxide of Ti to generate a strong intermolecular force between the adhesive layer and resin. The amount of Ti in the adhesive layer is preferably 3 to 200 mg/m2 per one surface. When the Ti amount is 3 mg/m2 or more and 200 mg/m2 or less, the effect of improving wet resin adhesion is sufficiently obtained. When the Ti amount is greater than 200 mg/m2, a further improvement of wet resin adhesion is not obtained and high cost arises. The amount of Ti in the adhesive layer can be determined by X-ray fluorescence surface analysis. The amount of 0 therein is not particularly limited and the presence of 0 can be confirmed by surface analysis using an XPS (X-ray photoelectron spectrometer). In order to achieve more excellent wet resin adhesion, the adhesive layer preferably has a thickness of 20 to 800 nm and also has bumps arranged with a line density of one or more per µm. When the thickness thereof is 20 nm or more, more excellent wet resin adhesion is achieved. When the thickness thereof is 800 nm or less, the adhesive layer is not fragile and has excellent wet resin adhesion. The reason why the presence of the bumps, arranged with a line density of one or more per µm, in the adhesive layer leads to an increase in wet resin adhesion is probably as described below. Figs. 1A and 1B each schematically show an adhesive layer, in cross section, included in a surface-treated steel sheet according to a preferred embodiment of the present invention. The adhesive layer has bumps which are uniformly and densely arranged. In particular, the bumps are arranged with a line density of one or more per µm; hence, the adhesive layer has an increased surface area and an increased contact area with resin as compared to layers, included in surface-treated steel sheets schematically shown in Figs. 2A and 2B, having nonuniform, sparse bumps. The presence of the bumps uniformly and densely arranged leads to an increase in an anchoring effect. Therefore, extremely excellent wet resin adhesion is achieved. When the line density of the bumps is less than one per µm, the contact area with resin is small and the anchoring effect is insufficient. Therefore, the above effect is not exhibited and the effect of increasing wet resin adhesion is small. Figs. 3A and 3B show results obtained by observing thin-film samples with a TEM (transmission electron microscope), the thin- film samples being prepared by processing a cross-sectional surface of a surface-treated steel sheet of an example (No. 8 of an example below) and a cross-sectional surface of a surface- treated steel sheet of a comparative example (No. 1 of a comparative example below) by a focused ion beam (FIB) process. The sample shown in Fig. 3A has a layer having bumps which are more uniformly and densely arranged as compared to those shown in Fig. 3B. The thickness of an adhesive layer and the line density of bumps of the adhesive layer are defined on the basis of a cross- sectional profile of the adhesive layer, observed with a TEM, shown in Fig. 3A or 3B as described below. Any cross-sectional profile of the adhesive layer observed in an arbitrary in-plane direction of the adhesive layer can be used herein. Fig. 4 is a schematic view illustrating the thickness of an adhesive layer of a surface-treated steel sheet according to the present invention and the line density of bumps of the adhesive layer. The thickness of the adhesive layer is defined as the maximum height H from the lower surface of the adhesive layer to the bumps in a cross-sectional profile of the layer observed with a TEM. The line density of the bumps is defined as the number of the bumps per unit length, the number thereof being determined on the assumption that one of the bumps is present when one or more intersections of an upper-level horizontal line and a profile curve are present between two intersections of a lower-level horizontal line and the profile curve, the upper- and lower-level horizontal lines being +10 nm apart from a center line located at a position given by the formula (H + L) / 2, wherein L represents the minimum height from the lower surface of the adhesive layer to the bottom of one of recessed portions. The thickness of the adhesive layer may be determined in such a manner that the highest protruding portion is selected from the TEM cross-sectional profile of the layer and the height from the lower surface of the layer is measured. The minimum height L from the lower surface of the adhesive layer to the bottom of one of the recessed portions may be determined in such a manner that the deepest recessed portion is selected from the cross-sectional profile of the layer and the height from the lower surface of the layer to the bottom of the deepest recessed portion is measured. In the present invention, the distribution of bumps present in an adhesive layer can be defined as an area density of 16 or more per µm2 in such a manner that a surface image of the adhesive layer observed with a SEM is three-dimensionally analyzed. Figs. 5A and 5B show a SEM image of an example (No. 8 of an example below) of the present invention and a SEM image of a comparative example (No. 1 of a comparative example below), respectively. The example shown in Fig. 5A has a layer having bumps which are more uniformly and densely arranged as compared to those of the comparative example shown in Fig. 5B. The presence of the uniformly and densely arranged bumps leads to an increase in surface area, an increase in contact area with resin, and an increase in anchoring effect due to the recessed and bumps as described above; hence, extremely excellent wet resin adhesion is probably achieved. The area density of the bumps in the adhesive layer can be determined to be the number of the bumps that are 0.005 µm higher than an average line of the recessed and bumps that is determined in such a manner that the SEM image (a 6 µm x 4.5 µm region) shown in Fig. 5A or 5B is three-dimensionally analyzed and swells are eliminated by filtering at a cut-off wavelength of 1.0 µm. For the density of the bumps in the adhesive layer, the line density determined from the cross-sectional profile of the TEM cross-sectional profile of the layer and the area density determined by three-dimensionally analyzing the SEM surface image of the layer are separately specified above. The reason for this is that the former has a problem that it takes a long time to prepare or measure a sample although the adhesive layer can be directly observed and the latter is simple and speedy in measurement although it takes a long time to remove a resin layer when the resin layer is present on the layer. According to the present invention, it has been confirmed that the wet resin adhesion defined by the line density is equivalent to that defined by the area density. The ratio (Rq / Ra) of Rq to Ra is preferably 1.3 or less because the distribution of the bumps is uniform and dense, Rq and Ra being specified in JIS B 0601: 2201 and being determined in such a manner that a cross-sectional curve is derived from three- dimensional data obtained with a SEM and then filtered at a cut- off wavelength of 1.0 urn. Furthermore, Rsk or Rku is preferably 0.6 or less or four or less, respectively, because the adhesive layer has a large surface area when being coated with resin, endures a pressure for forming a rigid interface, and exhibits an anchoring effect, Rsk and Rku being specified in JIS B 0601: 2201 and being determined in such a manner that a cross-sectional curve is derived from three-dimensional data obtained with a SEM and then filtered at a cut-off wavelength of 1.0 (am. A process for forming the adhesive layer is preferably as follows: a steel sheet coated with a corrosion-resistant layer is cathodically electrolyzed or immersed in an aqueous solution containing Ti and ions of at least one selected from the group consisting of Co, Fe, Ni, V, Cu, Mn, and Zn. Preferred examples of an aqueous solution containing Ti include aqueous solutions containing fluorotitanate ions and aqueous solutions containing fluorotitanate ions and fluorides. Examples of compounds producing fluorotitanate ions include fluorotitanic acid, ammonium fluorotitanate, and potassium fluorotitanate. Examples of the fluorides include sodium fluoride, potassium fluoride, silver fluoride, and tin fluoride. In particular, the steel sheet coated with the corrosion-resistant layer is preferably cathodically electrolyzed in an aqueous solution containing potassium fluorotitanate or an aqueous solution containing potassium fluorotitanate and sodium fluoride, because the adhesive layer can be uniformly formed with high efficiency. Examples of compounds producing ions of Co, Fe, Ni, V, Cu, Mn, or Zn include cobalt sulfate, cobalt chloride, iron sulfate, iron chloride, nickel sulfate, copper sulfate, vanadium oxysulfate, zinc sulfate, and manganese sulfate. The mass ratio of the metal ions to the Ti ions in the aqueous solution may be adjusted such that the mass ratio of the metal elements to Ti in the adhesive layer is 0.01 to ten. The current density and electrolysis time of cathodic electrolysis or the time of immersion may be appropriately determined depending on the necessary amount of Ti. The content of the metal elements in the layer can be measured by energy-dispersive x-ray analysis (EDX) or electron energy loss spectroscopy (EELS) in TEM observation as described above. The corrosion-resistant layer includes at least one selected from the group consisting of a Ni layer, a Sn layer, a Fe-Ni alloy layer, a Fe-Sn alloy layer, and a Fe-Ni-Sn alloy layer. After the corrosion-resistant layer is formed on at least one surface of the steel sheet, the adhesive layer is formed on the corrosion- resistant layer. This allows the surface-treated steel sheet to have increased corrosion resistance. The corrosion-resistant layer, which is disposed on the steel sheet, needs to include the Ni layer, the Sn layer, the Fe-Ni alloy layer, the Fe-Sn alloy layer, the Fe-Ni-Sn alloy layer, or some of these layers so as to be tightly bonded to the steel sheet and so as to allow the steel sheet to have excellent corrosion resistance even if resin is partly peeled from the steel sheet by scratching or the like. The corrosion-resistant layer can be formed by a known process depending on a metal element contained therein. (2) Resin-coated steel sheet (laminated steel sheet) A resin-coated steel sheet can be produced by coating the surface-treated steel sheet according to the present invention with resin. The surface-treated steel sheet according to the present invention has excellent wet resin adhesion as described above; hence, the resin-coated steel sheet has excellent corrosion resistance and work-ability. The resin used to coat the surface-treated steel sheet according to the present invention is not particularly limited and may be a resin film for lamination or a resin paint for painting. Examples of the resin include various thermoplastic resins and thermosetting resins. Examples of the resin film for lamination include olefin resin films made of polyethylene, polypropylene, ethylene-propylene copolymers, ethylene-vinyl acetate copolymers, ethylene-acrylic ester copolymers, ionomers, or the like; polyester films made of polybutylene terephthalate or the like; polyamide films made of nylon 6, nylon 66, nylon 11, nylon 12, or the like; and thermoplastic resin films such as polyvinyl chloride films and polyvinylidene chloride films. These films may be unstretched or biaxially stretched. Preferred examples of an adhesive used for lamination (laminate) include urethane adhesives, epoxy adhesives, acid-modified olefin resin adhesives, copolyamide adhesives, and copolyester adhesives (a thickness of 0.1 to 5.0 µm) . A thermosetting lacquer may be applied onto the surface- treated steel sheet or the film so as to form a layer with a thickness of 0.05 to 2 (am. Examples of the lacquering include thermoplastic and thermosetting paints such as modified epoxy paints including phenol epoxy paints and amino-epoxy paints; vinyl chloride-vinyl acetate copolymers; saponified vinyl chloride-vinyl acetate copolymers; vinyl chloride-vinyl acetate-maleic anhydride copolymers; vinyl paints; modified vinyl paints including epoxy- modified vinyl paints, epoxy amino-modified vinyl paints, and epoxy phenol-modified vinyl paints; acrylic paints; and synthetic rubber paints including styrene-butadiene copolymers. These lacquers may be used alone or in combination. In the present invention, a resin layer preferably has a thickness of 3 to 50 µm and more preferably 5 to 40 µm. When the thickness thereof is less than the above range, the corrosion resistance thereof is insufficient. When the thickness thereof is greater than the above range, a work-ability problem is likely to occur. In the present invention, the resin layer can be formed on or above the surface-treated steel sheet by an arbitrary process. When the surface-treated steel sheet is coated with resin by lamination, the following process can be used: for example, an extrusion-coating process, a cast film heat-bonding process, or a biaxially stretched film heat-bonding process. For the extrusion- coating process, the surface-treated steel sheet may be extrusion- coated with molten resin, which is then heat-bonded thereto. That is, resin is melted and kneaded in an extruder and then extruded into a thin film from a T-die, the extruded molten thin film is fed between a pair of lamination rollers together with the surface-treated steel sheet, and the thin film and the surface- treated steel sheet are pressed against each other under cooling conditions so as to be unified and are then quenched. In the case where a multilayer resin coating is formed by extrusion coating, a plurality of extruders for sub-layers are used and flows of resins are discharged from the extruders, are joined in a multilayer die, and may then be subjected to extrusion coating in the same manner as that used for a single-layer resin. Alternatively, the surface- treated steel sheet is fed perpendicularly to a pair of lamination rollers and a molten resin web is supplied to both sides thereof, whereby resin coating layers can be formed on both surfaces of the surface-treated steel sheet. The resin-coated steel sheet produced as described above can be used for three-piece cans with side seams and seamless cans (two-piece cans). The resin-coated steel sheet can be used for lids of stay-on-tab type easy-open cans and lids of full open type easy-open cans. Described above are merely examples of embodiments of the present invention. Various modifications may be made within the scopes of the claims. (3) Method for producing surface-treated steel sheet A producing method according to the present invention is as described below: a corrosion-resistant layer including at least one selected from the group consisting of a Ni layer, a Sn layer, a Fe-Ni alloy layer, a Fe-Sn alloy layer, and a Fe-Ni-Sn alloy layer is formed on at least one side of a steel sheet and an adhesive layer is formed on the corrosion-resistant layer in such a manner that the steel sheet is cathodically electrolyzed in an aqueous solution containing ions of Ti and ions of at least one selected from the group consisting of Co, Fe, Ni, V, Cu, Mn, and Zn. The adhesive layer can be formed in such a manner that the steel sheet is cathodically electrolyzed in the aqueous solution, which contains the Ti ions and the ions of at least one selected from the group consisting of Co, Fe, Ni, V, Cu, Mn, and Zn. The content of Ti in the aqueous solution is preferably 0.008 to 0.07 mol/1 and more preferably 0.02 to 0.05 mol/1. The molar ratio of at least one selected from the group consisting of Co, Fe, Ni, V, Cu, Mn, and Zn to Ti in the aqueous solution is preferably 0.01 to 10 and more preferably 0.1 to 2.5, because the adhesive layer can be formed so as to have surface irregularities densely and uniformly distributed and excellent wet resin adhesion is achieved. Preferred examples of an aqueous solution containing Ti include aqueous solutions containing fluorotitanate ions and aqueous solutions containing fluorotitanate ions and fluorides. Examples of compounds producing the fluorotitanate ions include fluorotitanic acid, ammonium fluorotitanate, and potassium fluorotitanate. Examples of the fluorides include sodium fluoride, potassium fluoride, silver fluoride, and tin fluoride. In particular, the steel sheet coated with the corrosion-resistant layer is preferably cathodically electrolyzed in an aqueous solution containing potassium fluorotitanate or an aqueous solution containing potassium fluorotitanate and sodium fluoride, because the layer can be uniformly formed with high efficiency. Examples of compounds producing ions of Co, Fe, Ni, V, Cu, Mn, or Zn include cobalt sulfate, cobalt chloride, iron sulfate, iron chloride, nickel sulfate, copper sulfate, vanadium oxysulfate, zinc sulfate, and manganese sulfate. In order to allow the content of Ti in the aqueous solution to be 0.008 to 0.07 mol/1 and preferably 0.02 to 0.05 mol/1 and in order to allow the molar ratio of at least one selected from the group consisting of Co, Fe, Ni, V, Cu, Mn, and Zn to Ti to be 0.01 to 10 and preferably 0.1 to 2.5, the mass ratio of Ti to at least one of these metals in the aqueous solution may be adjusted. In cathodic electrolysis, the current density and the electrolysis time are preferably 5 to 20 A/dm2 and 2 to 10 sec, respectively. Examples Corrosion-resistant layers are formed on both surfaces of each cold-rolled low-carbon steel sheet (a thickness of 0.2 mm) used to produce a tin-free steel sheet by one of Processes A to D below in Plating Bath a or b shown in Fig. 1 (Nos. 30 and 31 are excluded). A: A cold-rolled steel sheet is annealed at about 700°C, temper- rolled at an elongation rate of 1.5%, degreased by alkali electrolysis, pickled with sulfuric acid, and then plated with Ni in Plating Bath a, whereby corrosion-resistant layers including Ni layers are formed. B: A cold-rolled steel sheet is degreased by alkali electrolysis, plated with Ni in Plating Bath a, annealed at about 700°C in an atmosphere containing ten volume percent H2 and 90 volume percent N2 such that Ni platings diffuse to permeate the steel sheet, and then temper-rolled at an elongation rate of 1.5%, whereby corrosion-resistant layers including Fe-Ni alloy layers are formed. C: A cold-rolled steel sheet is degreased by alkali electrolysis, plated with Ni in Plating Bath a, annealed at about 700°C in an atmosphere containing ten volume percent H2 and 90 volume percent N2 such that Ni platings diffuse to permeate the steel sheet, temper-rolled at an elongation rate of 1.5%, degreased, pickled, plated with Sn in Plating Bath b, and then subjected to heat melting by heating the steel sheet to a temperature higher than the melting point of tin. This process allows corrosion-resistant layers including Fe-Ni-Sn alloy layers and Sn layers disposed thereon to be formed. D: A cold-rolled steel sheet is degreased by alkali electrolysis, annealed under the same conditions as Conditions A, temper-rolled under the same conditions as Conditions A, plated with Sn in Plating Bath b, and then subjected to heat melting by heating the steel sheet to a temperature higher than the melting point of tin. This process allows corrosion-resistant layers including Fe-Sn alloy layers and Sn layers disposed thereon to be formed. In Processes C and D, the Sn platings are partly alloyed. The net amount of Sn remaining without being alloyed is shown in Tables 3 and 4 together with the amount of Ni and the amount of Sn in each corrosion-resistant layer. The corrosion-resistant layers formed on both surfaces of each steel sheet are cathodically electrolyzed under conditions shown in Tables 2 to 4 and then dried such that adhesive layers are formed on the corrosion-resistant layers, whereby Surface-treated Steel Sheet Nos. 1 to 31 shown in Tables 2 to 4 are prepared. The adhesive layers of Surface-treated Steel Sheet Nos. 1, 16, 19, 22, and 29 contain none of Co, Fe, Ni, V, Cu, Mn, and Zn and therefore these sheets are comparative examples. The amount of Ti in each adhesive layers is determined by X- ray fluorescence spectrometry in comparison with a calibration sheet in which the amount of each deposited metal is determined by chemical analysis in advance. The amount of deposited Co, Fe, Ni, V, Cu, Mn, and Zn is determined by a technique selected from the group consisting of the same X-ray fluorescence spectrometry as that used to determine the amount of Ti, chemical analysis, Auger electron spectroscopy, and secondary ion mass spectrometry. The mass ratio of Co, Fe, Ni, V, Cu, Mn, and Zn to that of Ti in the adhesive layer is then evaluated. The presence of O in each of Surface-treated Steel Sheet Nos. 1 to 31 can be confirmed by XPS surface analysis. For some of the surface-treated steel sheets, the thickness of each adhesive layer and the line density of bumps are measured in such a manner that a thin film sample is prepared by processing a cross-sectional surface of the layer using an FIB and a cross- sectional profile of the sample is observed with a TEM. In this operation, an evaluation region of the sample is determined by SEM observation in advance, a protective layer is formed thereon, and the thin film sample is prepared by processing the cross-sectional surface using the FIB and Ga ions so as to have a thickness of about 0.1 µm and is then observed with the TEM. In the present invention, the FIB is obtained with SMI-3050 MS2 manufactured by SII-NT and the TEM is JEM-2010F manufactured by JOEL Ltd. A SEM image is obtained with a SEM that can measure the shape of irregularities. In the present invention, a high-resolution SEM, ERA-8800FE, manufactured by Elionix Inc. is used. This instrument includes four secondary electron detectors and can display an image in which a difference in composition is emphasized or an image which shows irregularities viewed in a specific direction from sum signals and/or difference signals of secondary electrons. The adhesive layers of some of the surface-treated steel sheets are calculated for Rq, Ra, Rsk, and Rku on the basis of obtained SEM images using an image-processing program attached to this instrument. The area density of bumps is calculated in such a manner that the SEM image obtained with the SEM is analyzed using a three-dimensional surface analyzing program, "SUMMIT", developed by Yanagi laboratory in Nagaoka University of Technology. Au is vapor-deposited on each sample to a thickness of about 10 nm in advance of observation. The resulting sample is observed with the SEM at a magnification of 20000 times and an acceleration voltage of 5 kV. The sample is analyzed in arbitrary five fields of view and the obtained data is averaged, whereby the area density of the bumps and the like are determined. For the calculation of Rq, Ra, Rsk, and Rku, 100 or more cross-sectional curves are taken in each field of view and evaluation values are obtained by averaging values determined by evaluating roughness curves extracted' from the cross-sectional curves and then averaged in five fields of view. Films which are made of polyethylene terephthalate copolymerized with isophthalic acid and which have the following properties are prepared: a draw ratio of 3.1 x 3.1, a thickness of 25 µm, a copolymerization ratio of 12 mole percent, and a melting point of 224°C. The films are laminated on both surfaces of each of Surface-treated Steel Sheet Nos. 1 to 31 such that the degree of biaxial orientation (BO value) of the films is 150 under the following lamination conditions: a steel sheet feed rate of 40 m/min, a nip length of 17 mm, and a time lag between pressing and water cooling of one second. This allows Laminated Steel Sheet Nos. 1 to 31 to be prepared. The term "nip length" means the length of a contact portion of a rubber roller with each steel sheet in the feed direction of the steel sheet. Laminated Steel Sheet Nos. 1 to 31 are evaluated for wet resin adhesion as described below. Wet resin adhesion: Humid resin adhesion is evaluated by a 180° peeling test in a retort atmosphere having a temperature of 130°C and a relative humidity of 100%. The 180° peeling test is a film- stripping test in which a test piece (a size of 30 mm x 100 mm, the front and rear surfaces being each n = 1, each laminated steel sheet being n = 2) that includes a steel sheet 1 having a notched portion 3 and a film 2 attached thereto as shown in Fig. 6A is used, a weight 4 (100 g) is attached to an end of the test piece, and the test piece is folded 180° over the film 2 as shown in Fig. 6B and then left for 30 minutes. A strip length 5 shown in Fig. 6C is measured and then evaluated. The strip lengths (n = 2) of the front and rear surfaces of each laminated steel sheet are averaged. The smaller the strip length 5, the better the wet resin adhesion. When the strip length 5 is less than 10 mm, the test piece is evaluated to be excellent in wet resin adhesion as targeted in the present invention. The evaluation results are shown in Tables 5 and 6. Laminated Steel Sheet Nos. 2 to 15, 17, 18, 20, 21, and 23 to 28, which are examples of the present invention, have excellent wet resin adhesion. In contrast, Laminated Steel Sheet Nos. 1, 16, 19, 22, and 29, which are comparative examples, have poor wet resin adhesion. Industrial Applicability According to the present invention, a surface-treated steel sheet which contains no Cr and which is excellent in wet resin adhesion can be produced. The surface-treated steel sheet according to the present invention can be used as an alternative to a conventional tin-free steel sheet with no problem and can be used for containers for storing oils, organic solvents, or paints without being coated with resin. If a resin-coated steel sheet produced by coating the surface-treated steel sheet with resin is formed into cans or can lids and the cans or can lids are exposed to a retort atmosphere, no resin is peeled off. WE CLAIM 1. A surface-treated steel sheet comprising an adhesive layer which is disposed on at least one surface of the steel sheet and which contains Ti and at least one selected from the group consisting of Co, Fe, Ni, V, Cu, Mn, and Zn, the ratio of the total amount of Co, Fe, Ni, V, Cu, Mn, and Zn to the amount of Ti contained therein being 0.01 to ten on a mass basis. 2. The surface-treated steel sheet according to Claim 1, wherein the adhesive layer has a thickness of 20 to 800 nm and also has bumps arranged with a line density of one or more per µm, the thickness of the adhesive layer is defined as the maximum height H from the lower surface of the adhesive layer to the bumps in a cross-sectional profile of the layer observed with a transmission electron microscope (TEM), and the line density of the bumps is defined as the number of the bumps per unit length, the number thereof being determined on the assumption that one of the bumps is present when one or more intersections of an upper-level horizontal line and a profile curve are present between two intersections of a lower-level horizontal line and the profile curve, the upper- and lower-level horizontal lines being ±10 nm apart from a center line located at a position given by the formula (H + L) / 2, where L represents the minimum height from the lower surface of the adhesive layer to the bottom of a recessed portion. 3. The surface-treated steel sheet according to Claim 1, wherein the adhesive layer has a thickness of 20 to 800 nm and also has bumps arranged with an area density of 16 or more per µm2 and the area density of the bumps of the adhesive layer is defined as the number of the bumps that are 0.005 µm higher than an average line of the bumps and recessed portions, the average line being determined in such a manner that a SEM image of the layer observed with a scanning electron microscope (SEM) is three-dimensionally analyzed and filtered at a cut-off wavelength of 1.0 µm. 4. The surface-treated steel sheet according to Claim 3, wherein the ratio (Rq / Ra) of root-mean-square roughness (Rq) to arithmetic average roughness (Ra) is 1.3 or less, the root-mean-square roughness and the arithmetic average roughness being specified in JIS B 0601: 2201 and being determined in such a manner that a cross-sectional curve is derived from three-dimensional data obtained with a SEM and then filtered at a cut-off wavelength of 1.0 µm. 5. The surface-treated steel sheet according to Claim 3 or 4, wherein skewness (Rsk) is 0.6 or less or kurtosis (Rku) is four or less, the skewness and the kurtosis being specified in JIS B 0601: 2201 and being determined in such a manner that a cross-sectional curve is derived from three- dimensional data obtained with a SEM and then filtered at a cut-off wavelength of 1.0 µm. 6. A surface-treated steel sheet comprising an adhesive layer which is disposed on at least one surface of the steel sheet, which has a thickness of 20 to 800 nm, and which contains Ti, wherein the adhesive layer has bumps arranged with a line density of one or more per µm, the thickness of the adhesive layer is defined as the maximum height H from the lower surface of the adhesive layer to the bumps in a cross-sectional profile of the layer observed with a transmission electron microscope (TEM), and the line density of the bumps is defined as the number of the bumps per unit length, the number thereof being determined on the assumption that one of the bumps is present when one or more intersections of an upper-level horizontal line and a profile curve are present between two intersections of a lower-level horizontal line and the profile curve, the upper- and lower-level horizontal lines being +10 nm apart from a center line located at a position given by the formula (H + L) / 2, where L represents the minimum height from the lower surface of the adhesive layer to the bottom of a recessed portion. 7. A surface-treated steel sheet comprising an adhesive layer which is disposed on at least one surface of the steel sheet, which has a thickness of 20 to 800 nm, and which contains Ti, wherein the adhesive layer has bumps arranged with an area density of 16 or more per µm2 and the area density of the bumps of the adhesive layer is defined as the number of the bumps that are 0.005 urn higher than an average line of the bumps and recessed portions, the average line being determined in such a manner that a SEM image of the layer observed with a scanning electron microscope (SEM) is three-dimensionally analyzed and filtered at a cut-off wavelength of 1.0 µm. 8. The surface-treated steel sheet according to Claim 7, wherein the ratio (Rq / Ra) of root-mean-square roughness (Rq) to arithmetic average roughness (Ra) is 1.3 or less, the root-mean-square roughness and the arithmetic average roughness being specified in JIS B 0601: 2201 and being determined in such a manner that a cross-sectional curve is derived from three-dimensional data obtained with a SEM and then filtered at a cut-off wavelength of 1.0 µm. 9. The surface-treated steel sheet according to Claim 7 or 8, wherein skewness (Rsk) is 0.6 or less or kurtosis (Rku) is four or less, the skewness and the kurtosis being specified in JIS B 0601: 2201 and being determined in such a manner that a cross-sectional curve is derived from three- dimensional data obtained with a SEM and then filtered at a cut-off wavelength of 1.0 µm. 10. The surface-treated steel sheet according to any one of Claims 1 to 9, wherein the amount of Ti in the adhesive layer is 3 to 200 mg/m2 per one surface. 11. The surface-treated steel sheet according to any one of Claims 1 to 10, further comprising a corrosion-resistant layer which is disposed on at least one surface of the steel sheet; which includes at least one selected from the group consisting of a Ni layer, a Sn layer, a Fe-Ni alloy layer, a Fe-Sn alloy layer, and a Fe-Ni-Sn alloy layer; and which is disposed under the adhesive layer. 12. The surface-treated steel sheet according to any one of Claims 1 to 11, coated with resin. 13. A method for producing a surface-treated steel sheet, comprising forming a corrosion-resistant layer, including at least one selected from the group consisting of a Ni layer, a Sn layer, a Fe-Ni alloy layer, a Fe-Sn alloy layer, and a Fe-Ni-Sn alloy layer, on at least one surface of a steel sheet and forming an adhesive layer in such a manner that the resulting steel sheet is cathodically electrolyzed in an aqueous solution containing ions of Ti and ions of at least one selected from the group consisting of Co, Fe, Ni, V, Cu, Mn, and Zn. 14. The surface-treated steel sheet-producing method according to Claim 13, wherein the content of Ti in the aqueous solution is 0.008 to 0.07 mol/1 and the molar ratio of at least one selected from the group consisting of Co, Fe, Ni, V, Cu, Mn, and Zn to Ti in the aqueous solution is 0.01 to 10. 15. The surface-treated steel sheet-producing method according to Claim 13 or 14, wherein the amount of Ti in the adhesive layer is 3 to 200 mg/m2 per one surface. It is an object to provide a surface-treated steel sheet which contains no Cr, which is excellent in wet resin adhesion, and which can be used as an alternative to a conventional tin-free steel sheet and to provide a resin- coated steel sheet produced by coating the surface-treated steel sheet with resin. A surface-treated steel sheet including an adhesive layer which is disposed on at least one surface of the steel sheet and which contains Ti and at least one selected from the group consisting of Co, Fe, Ni, V, Cu, Mn, and Zn, the ratio of the total amount of Co, Fe, Ni, V, Cu, Mn, and Zn to the amount of Ti contained therein being 0.01 to ten on a mass basis, and a method for producing the surface-treated steel sheet. A surface-treated steel sheet including an adhesive layer which is disposed on at least one surface of the steel sheet, which has a thickness of 20 to 800 nm, which contains Ti, and which has bumps arranged with a line density of one or more per μm. The thickness of the adhesive layer is defined as the maximum height H from the lower surface of the adhesive layer to the bumps in a cross-sectional profile of the layer observed with a transmission electron microscope (TEM) . The line density of the bumps is defined as the number of the bumps per unit length, the number thereof being determined on the assumption that one of the bumps is

Full Text

DESCRIPTION
SURFACE-TREATED STEEL SHEET, METHOD FOR PRODUCING THE SAME, AND
RESIN-COATED STEEL SHEET
Technical Field
The present invention relates to surface-treated steel sheets
which are used principally for containers such as cans after being
coated with resin in such a manner that resin films or the like
are laminated on the surface-treated steel sheets or resin-
containing paints are applied onto the surface-treated steel
sheets. The present invention particularly relates to a surface-
treated steel sheet having high adhesion (hereinafter referred to
as wet resin adhesion) to resin applied thereto in a high-
temperature humid environment, a method for producing the surface-
treated steel sheet, and a resin-coated steel sheet produced by
coating the surface-treated steel sheet with resin.
The present invention further relates to a surface-treated
steel sheet that exhibits high corrosion resistance even if resin
applied thereto is peeled therefrom, a method for producing the
surface-treated steel sheet, and a resin-coated steel sheet
produced by coating the surface-treated steel sheet with resin.
Background Art
Tin-plated steel sheets and electrolytically chromated steel
sheets referred to as tin-free steel sheets are used for various
metal cans such as beverage cans, food cans, pail cans, and 18-
litter cans. In particular, the tin-free steel sheets are produced
by electrolyzing steel sheets in a plating bath containing
hexavalent chromium and have the advantage of having excellent wet
resin adhesion to resin such as paint.
In recent years, the use of hexavalent chromium has tended to
be restricted worldwide in response to growing environmental
awareness. Alternatives to the tin-free steel sheets, which are
produced using such a plating bath containing hexavalent chromium,
have been needed. For example, Japanese Unexamined Patent
Application Publication No. 2004-285380 discloses a steel sheet,
electrolyzed in a tungstic acid solution, for containers. Japanese
Unexamined Patent Application Publication No. 2001-220685
discloses a surface-treated steel sheet, coated with a phosphonate
layer, for containers. Japanese Unexamined Patent Application
Publication No. 2002-355921 discloses a steel sheet, coated with a
surface treatment layer containing one or both of Sn and Ni, for
containers, the surface treatment layer being overlaid with a
resin layer which contains one or both of tannic acid and acetic
acid and Ti, Zn, or one or more of compounds thereof and which has
a phenol structure. Japanese Unexamined Patent Application
Publication No. 2006-009046 discloses a surface-treated metal
material having an organic surface treatment layer and an
inorganic surface treatment layer which contains no phosphate ion
but principally contains T, 0, and/or F.
Various types of metal cans have been conventionally
manufactured in such a manner that metal sheets such as tin-free
steel sheets are painted and then formed into can bodies. In
recent years, the following method has been widely used to reduce
the amount of industrial waste: a method in which a resin-coated
metal sheet that is not painted but is coated with resin such as a
resin film is formed into a can body. For the resin-coated metal
sheet, the resin needs to strongly adhere to the metal sheet. In
particular, resin-coated metal sheets used for beverage or food
cans need to have high wet resin adhesion such that no resin is
peeled therefrom even in high-temperature humid environments,
because the beverage or food cans are subjected to retort
sterilization steps in some cases after contents are packed in the
beverage or food cans.
Furthermore, the resin-coated metal sheets need to have high
corrosion resistance such that the cans are prevented from being
perforated by corrosion due to the contents of the cans even if
resin is partly peeled from the cans by scratching.
The following sheets and material have insufficient wet resin
adhesion when being used in a retort atmosphere: the steel sheet
electrolyzed in the tungstic acid solution as disclosed in
Japanese Unexamined Patent Application Publication No. 2004-285380,
the surface-treated steel sheet coated with the phosphonate layer
as disclosed in Japanese Unexamined Patent Application Publication
No. 2001-220685, the steel sheet having the resin layer having the
phenol structure as disclosed in Japanese Unexamined Patent
Application Publication No. 2002-355921, and the surface-treated
metal material having the organic surface treatment layer and the
inorganic surface treatment layer principally containing T, 0,
and/or F as disclosed in Japanese Unexamined Patent Application
Publication No. 2006-009046.
It is an object of the present invention to provide a surface-
treated steel sheet which contains no Cr, which has excellent wet
resin adhesion, and which can be used as an alternative to a tin-
free steel sheet; a method for producing the surface-treated steel
sheet; and a resin-coated steel sheet produced by coating the
surface-treated steel sheet with resin.
Disclosure of Invention
The scope of the present invention is as described below.
1. A surface-treated steel sheet includes an adhesive layer which
is disposed on at least one surface of the steel sheet and which
contains Ti and at least one selected from the group consisting of
Co, Fe, Ni, V, Cu, Mn, and Zn. The ratio of the total amount of Co,
Fe, Ni, V, Cu, Mn, and Zn to the amount of Ti contained therein is
0.01 to ten on a mass basis.
2. In the surface-treated steel sheet specified in Item 1, the
adhesive layer has a thickness of 20 to 800 nm and also has bumps
arranged with a line density of one or more per µm, the thickness
of the adhesive layer is defined as the maximum height H from the
lower surface of the adhesive layer to the bumps in a cross-
sectional profile of the layer observed with a transmission
electron microscope (TEM), and the line density of the bumps is
defined as the number of the bumps per unit length. The number
thereof is determined on the assumption that one of the bumps is
present when one or more intersections of an upper-level
horizontal line and a profile curve are present between two
intersections of a lower-level horizontal line and the profile
curve. The upper- and lower-level horizontal lines are ±10 nm
apart from a center line located at a position given by the
formula (H + L) / 2, where L represents the minimum height from
the lower surface of the adhesive layer to the bottom of a
recessed portion.
3. In the surface-treated steel sheet specified in Item 1, the
adhesive layer has a thickness of 20 to 800 nm and also has bumps
arranged with an area density of 16 or more per µm2 and the area
density of the bumps of the adhesive layer is defined as the
number of the bumps that are 0.005 µm higher than an average line
of the bumps and recessed portions. The average line is determined
in such a manner that a SEM image of the layer observed with a
scanning electron microscope (SEM) is three-dimensionally analyzed
and filtered at a cut-off wavelength of 1.0 µm.
4. In the surface-treated steel sheet specified in Item 3, the
ratio (Rq / Ra) of root-mean-square roughness (Rq) to arithmetic
average roughness (Ra) is 1.3 or less. The root-mean-square
roughness and the arithmetic average roughness are specified in
JIS B 0601: 2201 and determined in such a manner that a cross-
sectional curve is derived from three-dimensional data obtained
with a SEM and then filtered at a cut-off wavelength of 1.0 µm.
5. In the surface-treated steel sheet specified in Item 3 or 4,
skewness (Rsk) is 0.6 or less or kurtosis (Rku) is four or less.
The skewness and the kurtosis are specified in JIS B 0601: 2201
and determined in such a manner that a cross-sectional curve is
derived from three-dimensional data obtained with a SEM and then
filtered at a cut-off wavelength of 1.0 µm.
6. A surface-treated steel sheet includes an adhesive layer which
is disposed on at least one surface of the steel sheet, which has
a thickness of 20 to 800 nm, which contains Ti, and which has
bumps arranged with a line density of one or more per µm. The
thickness of the adhesive layer is defined as the maximum height H
from the lower surface of the adhesive layer to the bumps in a
cross-sectional profile of the layer observed with a transmission
electron microscope (TEM). The line density of the bumps is
defined as the number of the bumps per unit length. The number
thereof is determined on the assumption that one of the bumps is
present when one or more intersections of an upper-level
horizontal line and a profile curve are present between two
intersections of a lower-level horizontal line and the profile
curve. The upper- and lower-level horizontal lines are ±10 nm
apart from a center line located at a position given by the
formula (H + L) / 2, where L represents the minimum height from
the lower surface of the adhesive layer to the bottom of a
recessed portion.
7. A surface-treated steel sheet includes an adhesive layer which
is disposed on at least one surface of the steel sheet, which has
a thickness of 20 to 800 nm, which contains Ti, and which has
bumps arranged with an area density of 16 or more per urn2. The
area density of the bumps of the adhesive layer is defined as the
number of the bumps that are 0.005 µm higher than an average line
of the bumps and recessed portions. The average line is determined
in such a manner that a SEM image of the layer observed with a
scanning electron microscope (SEM) is three-dimensionally analyzed
and filtered at a cut-off wavelength of 1.0 |im.
8. In the surface-treated steel sheet specified in Item 7, the
ratio (Rq / Ra) of root-mean-square roughness (Rq) to arithmetic
average roughness (Ra) is 1.3 or less. The root-mean-square
roughness and the arithmetic average roughness are specified in
JIS B 0601: 2201 and determined in such a manner that a cross-
sectional curve is derived from three-dimensional data obtained
with a SEM and then filtered at a cut-off wavelength of 1.0 µm.
9. In the surface-treated steel sheet specified in Item 7 or 8,
skewness (Rsk) is 0.6 or less or kurtosis (Rku) is four or less.
The skewness and the kurtosis are specified in JIS B 0601: 2201
and determined in such a manner that a cross-sectional curve is
derived from three-dimensional data obtained with a SEM and then
filtered at a cut-off wavelength of 1.0 µm.
10. In the surface-treated steel sheet specified in any one of
Items 1 to 9, the amount of Ti in the adhesive layer is 3 to 200
mg/m2 per one surface.
11. The surface-treated steel sheet specified in any one of Items
1 to 10 further includes a corrosion-resistant layer which is
disposed on at least one surface of the steel sheet; which
includes at least one selected from the group consisting of a Ni
layer, a Sn layer, a Fe-Ni alloy layer, a Fe-Sn alloy layer, and a
Fe-Ni-Sn alloy layer; and which is disposed under the adhesive
layer.
12. The surface-treated steel sheet specified in any one of Items
1 to 11 is coated with resin.
13. A method for producing a surface-treated steel sheet includes
forming a corrosion-resistant layer, including at least one
selected from the group consisting of a Ni layer, a Sn layer, a
Fe-Ni alloy layer, a Fe-Sn alloy layer, and a Fe-Ni-Sn alloy layer,
on at least one surface of a steel sheet and also includes forming
an adhesive layer in such a manner that the resulting steel sheet
is cathodically electrolyzed in an aqueous solution containing
ions of Ti and ions of at least one selected from the group
consisting of Co, Fe, Ni, V, Cu, Mn, and Zn.
14. In the surface-treated steel sheet-producing method specified
in Item 13, the content of Ti in the aqueous solution is 0.008 to
0.07 mol/1 and the molar ratio of at least one selected from the
group consisting of Co, Fe, Ni, V, Cu, Mn, and Zn to Ti in the
aqueous solution is 0.01 to 10.
15. In the surface-treated steel sheet-producing method specified
in Item 13 or 14, the amount of Ti in the adhesive layer is 3 to
200 mg/m2 per one surface.
Brief Description of Drawings
Figs. 1A and 1B are schematic sectional views of adhesive
layers included in surface-treated steel sheets according to the
present invention.
Figs. 2A and 2B are schematic sectional views of adhesive
layers included in surface-treated steel sheets of comparative
examples.
Figs. 3A and 3B are images illustrating the TEM observation
results of a cross-sectional surface of an adhesive layer of an
example of the present invention and a cross-sectional surface of
a layer of a comparative example.
Fig. 4 is a schematic view illustrating the thickness of an
adhesive layer included in a surface-treated steel sheet according
to the present invention and the line density of bumps of the
adhesive layer.
Figs. 5A and 5B are images illustrating the SEM observation
results of an adhesive layer of an example of the present
invention and a layer of a comparative example.
Figs. 6A, 6B, and 6C are illustrations showing a 180° peeling
test.
[Reference Numerals]
1 steel sheet
2 film
3 notched portion of steel sheet
4 weight
5 peeled length
Best Modes for Carrying Out the Invention
The inventors have conducted intensive research on surface-
treated steel sheets which contain no Cr, which have excellent wet
resin adhesion, and which can be used as alternatives to tin-free
steel sheets and have then obtained findings below.
(1) Extremely excellent wet resin adhesion can be achieved by
forming an adhesive layer containing Ti and an element such as Co,
Fe, Ni, V, Cu, Mn, or Zn on a steel sheet.
(2) In order to achieve extremely excellent wet resin
adhesion, an adhesive layer having a large number of fine bumps
arranged uniformly is preferably formed.
The present invention has been made on the basis of these
findings. The contents of the present invention will now be
described in detail.
(1) Surface-treated steel sheet
A surface-treated steel sheet according to the present
invention includes an adhesive layer which is disposed on at least
one surface of the surface-treated steel sheet and which contains
Ti and at least one selected from the group consisting of Co, Fe,
Ni, V, Cu, Mn, and Zn.
An ordinary steel sheet, such as a low-carbon steel sheet or
an ultra-low-carbon steel sheet, for cans can be used as a raw
steel sheet.
A steel sheet coated with an adhesive layer containing Ti or
an adhesive layer which contains Ti and at least one selected from
the group consisting of Co, Fe, Ni, V, Cu, Mn, and Zn has
excellent wet resin adhesion.
The reason for this is unclear at present and is probably that
a strong intermolecular force is present between resin and a layer
which is composed of an oxide of Ti and which has high molecular
weight or that the above metal element is taken in the layer
containing Ti and therefore the layer has surface irregularities
which are densely and uniformly distributed.
The ratio of the total amount of Co, Fe, Ni, V, Cu, Mn, and Zn
to the amount of Ti in the adhesive layer needs to be 0.01 to ten
on a mass basis. This allows the adhesive layer to have surface
irregularities which are densely and uniformly distributed,
thereby achieving excellent wet resin adhesion. The mass ratio
thereof is preferably 0.1 to two. The content of the metal
elements in the adhesive layer can be determined by energy-
dispersive x-ray analysis (EDX) or electron energy loss
spectroscopy (EELS) in TEM observation below.
In view of an increase in wet resin adhesion, the adhesive
layer preferably further contains 0. The presence of 0 probably
allows the adhesive layer to be composed of an oxide of Ti to
generate a strong intermolecular force between the adhesive layer
and resin.
The amount of Ti in the adhesive layer is preferably 3 to 200
mg/m2 per one surface. When the Ti amount is 3 mg/m2 or more and
200 mg/m2 or less, the effect of improving wet resin adhesion is
sufficiently obtained. When the Ti amount is greater than 200
mg/m2, a further improvement of wet resin adhesion is not obtained
and high cost arises. The amount of Ti in the adhesive layer can
be determined by X-ray fluorescence surface analysis. The amount
of 0 therein is not particularly limited and the presence of 0 can
be confirmed by surface analysis using an XPS (X-ray photoelectron
spectrometer).
In order to achieve more excellent wet resin adhesion, the
adhesive layer preferably has a thickness of 20 to 800 nm and also
has bumps arranged with a line density of one or more per µm. When
the thickness thereof is 20 nm or more, more excellent wet resin
adhesion is achieved. When the thickness thereof is 800 nm or less,
the adhesive layer is not fragile and has excellent wet resin
adhesion.
The reason why the presence of the bumps, arranged with a line
density of one or more per µm, in the adhesive layer leads to an
increase in wet resin adhesion is probably as described below.
Figs. 1A and 1B each schematically show an adhesive layer, in
cross section, included in a surface-treated steel sheet according
to a preferred embodiment of the present invention. The adhesive
layer has bumps which are uniformly and densely arranged. In
particular, the bumps are arranged with a line density of one or
more per µm; hence, the adhesive layer has an increased surface
area and an increased contact area with resin as compared to
layers, included in surface-treated steel sheets schematically
shown in Figs. 2A and 2B, having nonuniform, sparse bumps. The
presence of the bumps uniformly and densely arranged leads to an
increase in an anchoring effect. Therefore, extremely excellent
wet resin adhesion is achieved. When the line density of the bumps
is less than one per µm, the contact area with resin is small and
the anchoring effect is insufficient. Therefore, the above effect
is not exhibited and the effect of increasing wet resin adhesion
is small.
Figs. 3A and 3B show results obtained by observing thin-film
samples with a TEM (transmission electron microscope), the thin-
film samples being prepared by processing a cross-sectional
surface of a surface-treated steel sheet of an example (No. 8 of
an example below) and a cross-sectional surface of a surface-
treated steel sheet of a comparative example (No. 1 of a
comparative example below) by a focused ion beam (FIB) process.
The sample shown in Fig. 3A has a layer having bumps which are
more uniformly and densely arranged as compared to those shown in
Fig. 3B.
The thickness of an adhesive layer and the line density of
bumps of the adhesive layer are defined on the basis of a cross-
sectional profile of the adhesive layer, observed with a TEM,
shown in Fig. 3A or 3B as described below. Any cross-sectional
profile of the adhesive layer observed in an arbitrary in-plane
direction of the adhesive layer can be used herein.
Fig. 4 is a schematic view illustrating the thickness of an
adhesive layer of a surface-treated steel sheet according to the
present invention and the line density of bumps of the adhesive
layer. The thickness of the adhesive layer is defined as the
maximum height H from the lower surface of the adhesive layer to
the bumps in a cross-sectional profile of the layer observed with
a TEM. The line density of the bumps is defined as the number of
the bumps per unit length, the number thereof being determined on
the assumption that one of the bumps is present when one or more
intersections of an upper-level horizontal line and a profile
curve are present between two intersections of a lower-level
horizontal line and the profile curve, the upper- and lower-level
horizontal lines being +10 nm apart from a center line located at
a position given by the formula (H + L) / 2, wherein L represents
the minimum height from the lower surface of the adhesive layer to
the bottom of one of recessed portions.
The thickness of the adhesive layer may be determined in such
a manner that the highest protruding portion is selected from the
TEM cross-sectional profile of the layer and the height from the
lower surface of the layer is measured. The minimum height L from
the lower surface of the adhesive layer to the bottom of one of
the recessed portions may be determined in such a manner that the
deepest recessed portion is selected from the cross-sectional
profile of the layer and the height from the lower surface of the
layer to the bottom of the deepest recessed portion is measured.
In the present invention, the distribution of bumps present in
an adhesive layer can be defined as an area density of 16 or more
per µm2 in such a manner that a surface image of the adhesive layer
observed with a SEM is three-dimensionally analyzed. Figs. 5A and
5B show a SEM image of an example (No. 8 of an example below) of
the present invention and a SEM image of a comparative example (No.
1 of a comparative example below), respectively. The example shown
in Fig. 5A has a layer having bumps which are more uniformly and
densely arranged as compared to those of the comparative example
shown in Fig. 5B. The presence of the uniformly and densely
arranged bumps leads to an increase in surface area, an increase
in contact area with resin, and an increase in anchoring effect
due to the recessed and bumps as described above; hence, extremely
excellent wet resin adhesion is probably achieved.
The area density of the bumps in the adhesive layer can be
determined to be the number of the bumps that are 0.005 µm higher
than an average line of the recessed and bumps that is determined
in such a manner that the SEM image (a 6 µm x 4.5 µm region) shown
in Fig. 5A or 5B is three-dimensionally analyzed and swells are
eliminated by filtering at a cut-off wavelength of 1.0 µm.
For the density of the bumps in the adhesive layer, the line
density determined from the cross-sectional profile of the TEM
cross-sectional profile of the layer and the area density
determined by three-dimensionally analyzing the SEM surface image
of the layer are separately specified above. The reason for this
is that the former has a problem that it takes a long time to
prepare or measure a sample although the adhesive layer can be
directly observed and the latter is simple and speedy in
measurement although it takes a long time to remove a resin layer
when the resin layer is present on the layer. According to the
present invention, it has been confirmed that the wet resin
adhesion defined by the line density is equivalent to that defined
by the area density.
The ratio (Rq / Ra) of Rq to Ra is preferably 1.3 or less
because the distribution of the bumps is uniform and dense, Rq and
Ra being specified in JIS B 0601: 2201 and being determined in
such a manner that a cross-sectional curve is derived from three-
dimensional data obtained with a SEM and then filtered at a cut-
off wavelength of 1.0 urn. Furthermore, Rsk or Rku is preferably
0.6 or less or four or less, respectively, because the adhesive
layer has a large surface area when being coated with resin,
endures a pressure for forming a rigid interface, and exhibits an
anchoring effect, Rsk and Rku being specified in JIS B 0601: 2201
and being determined in such a manner that a cross-sectional curve
is derived from three-dimensional data obtained with a SEM and
then filtered at a cut-off wavelength of 1.0 (am.
A process for forming the adhesive layer is preferably as
follows: a steel sheet coated with a corrosion-resistant layer is
cathodically electrolyzed or immersed in an aqueous solution
containing Ti and ions of at least one selected from the group
consisting of Co, Fe, Ni, V, Cu, Mn, and Zn. Preferred examples of
an aqueous solution containing Ti include aqueous solutions
containing fluorotitanate ions and aqueous solutions containing
fluorotitanate ions and fluorides. Examples of compounds producing
fluorotitanate ions include fluorotitanic acid, ammonium
fluorotitanate, and potassium fluorotitanate. Examples of the
fluorides include sodium fluoride, potassium fluoride, silver
fluoride, and tin fluoride. In particular, the steel sheet coated
with the corrosion-resistant layer is preferably cathodically
electrolyzed in an aqueous solution containing potassium
fluorotitanate or an aqueous solution containing potassium
fluorotitanate and sodium fluoride, because the adhesive layer can
be uniformly formed with high efficiency.
Examples of compounds producing ions of Co, Fe, Ni, V, Cu, Mn,
or Zn include cobalt sulfate, cobalt chloride, iron sulfate, iron
chloride, nickel sulfate, copper sulfate, vanadium oxysulfate,
zinc sulfate, and manganese sulfate.
The mass ratio of the metal ions to the Ti ions in the aqueous
solution may be adjusted such that the mass ratio of the metal
elements to Ti in the adhesive layer is 0.01 to ten. The current
density and electrolysis time of cathodic electrolysis or the time
of immersion may be appropriately determined depending on the
necessary amount of Ti. The content of the metal elements in the
layer can be measured by energy-dispersive x-ray analysis (EDX) or
electron energy loss spectroscopy (EELS) in TEM observation as
described above.
The corrosion-resistant layer includes at least one selected
from the group consisting of a Ni layer, a Sn layer, a Fe-Ni alloy
layer, a Fe-Sn alloy layer, and a Fe-Ni-Sn alloy layer. After the
corrosion-resistant layer is formed on at least one surface of the
steel sheet, the adhesive layer is formed on the corrosion-
resistant layer. This allows the surface-treated steel sheet to
have increased corrosion resistance.
The corrosion-resistant layer, which is disposed on the steel
sheet, needs to include the Ni layer, the Sn layer, the Fe-Ni
alloy layer, the Fe-Sn alloy layer, the Fe-Ni-Sn alloy layer, or
some of these layers so as to be tightly bonded to the steel sheet
and so as to allow the steel sheet to have excellent corrosion
resistance even if resin is partly peeled from the steel sheet by
scratching or the like.
The corrosion-resistant layer can be formed by a known process
depending on a metal element contained therein.
(2) Resin-coated steel sheet (laminated steel sheet)
A resin-coated steel sheet can be produced by coating the
surface-treated steel sheet according to the present invention
with resin. The surface-treated steel sheet according to the
present invention has excellent wet resin adhesion as described
above; hence, the resin-coated steel sheet has excellent corrosion
resistance and work-ability.
The resin used to coat the surface-treated steel sheet
according to the present invention is not particularly limited and
may be a resin film for lamination or a resin paint for painting.
Examples of the resin include various thermoplastic resins and
thermosetting resins. Examples of the resin film for lamination
include olefin resin films made of polyethylene, polypropylene,
ethylene-propylene copolymers, ethylene-vinyl acetate copolymers,
ethylene-acrylic ester copolymers, ionomers, or the like;
polyester films made of polybutylene terephthalate or the like;
polyamide films made of nylon 6, nylon 66, nylon 11, nylon 12, or
the like; and thermoplastic resin films such as polyvinyl chloride
films and polyvinylidene chloride films. These films may be
unstretched or biaxially stretched. Preferred examples of an
adhesive used for lamination (laminate) include urethane adhesives,
epoxy adhesives, acid-modified olefin resin adhesives, copolyamide
adhesives, and copolyester adhesives (a thickness of 0.1 to 5.0
µm) . A thermosetting lacquer may be applied onto the surface-
treated steel sheet or the film so as to form a layer with a
thickness of 0.05 to 2 (am.
Examples of the lacquering include thermoplastic and
thermosetting paints such as modified epoxy paints including
phenol epoxy paints and amino-epoxy paints; vinyl chloride-vinyl
acetate copolymers; saponified vinyl chloride-vinyl acetate
copolymers; vinyl chloride-vinyl acetate-maleic anhydride
copolymers; vinyl paints; modified vinyl paints including epoxy-
modified vinyl paints, epoxy amino-modified vinyl paints, and
epoxy phenol-modified vinyl paints; acrylic paints; and synthetic
rubber paints including styrene-butadiene copolymers. These
lacquers may be used alone or in combination.
In the present invention, a resin layer preferably has a
thickness of 3 to 50 µm and more preferably 5 to 40 µm. When the
thickness thereof is less than the above range, the corrosion
resistance thereof is insufficient. When the thickness thereof is
greater than the above range, a work-ability problem is likely to
occur.
In the present invention, the resin layer can be formed on or
above the surface-treated steel sheet by an arbitrary process.
When the surface-treated steel sheet is coated with resin by
lamination, the following process can be used: for example, an
extrusion-coating process, a cast film heat-bonding process, or a
biaxially stretched film heat-bonding process. For the extrusion-
coating process, the surface-treated steel sheet may be extrusion-
coated with molten resin, which is then heat-bonded thereto. That
is, resin is melted and kneaded in an extruder and then extruded
into a thin film from a T-die, the extruded molten thin film is
fed between a pair of lamination rollers together with the
surface-treated steel sheet, and the thin film and the surface-
treated steel sheet are pressed against each other under cooling
conditions so as to be unified and are then quenched. In the case
where a multilayer resin coating is formed by extrusion coating, a
plurality of extruders for sub-layers are used and flows of resins
are discharged from the extruders, are joined in a multilayer die,
and may then be subjected to extrusion coating in the same manner
as that used for a single-layer resin. Alternatively, the surface-
treated steel sheet is fed perpendicularly to a pair of lamination
rollers and a molten resin web is supplied to both sides thereof,
whereby resin coating layers can be formed on both surfaces of the
surface-treated steel sheet.
The resin-coated steel sheet produced as described above can
be used for three-piece cans with side seams and seamless cans
(two-piece cans). The resin-coated steel sheet can be used for
lids of stay-on-tab type easy-open cans and lids of full open type
easy-open cans.
Described above are merely examples of embodiments of the
present invention. Various modifications may be made within the
scopes of the claims.
(3) Method for producing surface-treated steel sheet
A producing method according to the present invention is as
described below: a corrosion-resistant layer including at least
one selected from the group consisting of a Ni layer, a Sn layer,
a Fe-Ni alloy layer, a Fe-Sn alloy layer, and a Fe-Ni-Sn alloy
layer is formed on at least one side of a steel sheet and an
adhesive layer is formed on the corrosion-resistant layer in such
a manner that the steel sheet is cathodically electrolyzed in an
aqueous solution containing ions of Ti and ions of at least one
selected from the group consisting of Co, Fe, Ni, V, Cu, Mn, and
Zn.
The adhesive layer can be formed in such a manner that the
steel sheet is cathodically electrolyzed in the aqueous solution,
which contains the Ti ions and the ions of at least one selected
from the group consisting of Co, Fe, Ni, V, Cu, Mn, and Zn. The
content of Ti in the aqueous solution is preferably 0.008 to 0.07
mol/1 and more preferably 0.02 to 0.05 mol/1. The molar ratio of
at least one selected from the group consisting of Co, Fe, Ni, V,
Cu, Mn, and Zn to Ti in the aqueous solution is preferably 0.01 to
10 and more preferably 0.1 to 2.5, because the adhesive layer can
be formed so as to have surface irregularities densely and
uniformly distributed and excellent wet resin adhesion is achieved.
Preferred examples of an aqueous solution containing Ti
include aqueous solutions containing fluorotitanate ions and
aqueous solutions containing fluorotitanate ions and fluorides.
Examples of compounds producing the fluorotitanate ions include
fluorotitanic acid, ammonium fluorotitanate, and potassium
fluorotitanate. Examples of the fluorides include sodium fluoride,
potassium fluoride, silver fluoride, and tin fluoride. In
particular, the steel sheet coated with the corrosion-resistant
layer is preferably cathodically electrolyzed in an aqueous
solution containing potassium fluorotitanate or an aqueous
solution containing potassium fluorotitanate and sodium fluoride,
because the layer can be uniformly formed with high efficiency.
Examples of compounds producing ions of Co, Fe, Ni, V, Cu, Mn,
or Zn include cobalt sulfate, cobalt chloride, iron sulfate, iron
chloride, nickel sulfate, copper sulfate, vanadium oxysulfate,
zinc sulfate, and manganese sulfate.
In order to allow the content of Ti in the aqueous solution to
be 0.008 to 0.07 mol/1 and preferably 0.02 to 0.05 mol/1 and in
order to allow the molar ratio of at least one selected from the
group consisting of Co, Fe, Ni, V, Cu, Mn, and Zn to Ti to be 0.01
to 10 and preferably 0.1 to 2.5, the mass ratio of Ti to at least
one of these metals in the aqueous solution may be adjusted. In
cathodic electrolysis, the current density and the electrolysis
time are preferably 5 to 20 A/dm2 and 2 to 10 sec, respectively.
Examples
Corrosion-resistant layers are formed on both surfaces of each
cold-rolled low-carbon steel sheet (a thickness of 0.2 mm) used to
produce a tin-free steel sheet by one of Processes A to D below in
Plating Bath a or b shown in Fig. 1 (Nos. 30 and 31 are excluded).
A: A cold-rolled steel sheet is annealed at about 700°C, temper-
rolled at an elongation rate of 1.5%, degreased by alkali
electrolysis, pickled with sulfuric acid, and then plated with Ni
in Plating Bath a, whereby corrosion-resistant layers including Ni
layers are formed.
B: A cold-rolled steel sheet is degreased by alkali electrolysis,
plated with Ni in Plating Bath a, annealed at about 700°C in an
atmosphere containing ten volume percent H2 and 90 volume percent
N2 such that Ni platings diffuse to permeate the steel sheet, and
then temper-rolled at an elongation rate of 1.5%, whereby
corrosion-resistant layers including Fe-Ni alloy layers are formed.
C: A cold-rolled steel sheet is degreased by alkali electrolysis,
plated with Ni in Plating Bath a, annealed at about 700°C in an
atmosphere containing ten volume percent H2 and 90 volume percent
N2 such that Ni platings diffuse to permeate the steel sheet,
temper-rolled at an elongation rate of 1.5%, degreased, pickled,
plated with Sn in Plating Bath b, and then subjected to heat
melting by heating the steel sheet to a temperature higher than
the melting point of tin. This process allows corrosion-resistant
layers including Fe-Ni-Sn alloy layers and Sn layers disposed
thereon to be formed.
D: A cold-rolled steel sheet is degreased by alkali electrolysis,
annealed under the same conditions as Conditions A, temper-rolled
under the same conditions as Conditions A, plated with Sn in
Plating Bath b, and then subjected to heat melting by heating the
steel sheet to a temperature higher than the melting point of tin.
This process allows corrosion-resistant layers including Fe-Sn
alloy layers and Sn layers disposed thereon to be formed.
In Processes C and D, the Sn platings are partly alloyed. The
net amount of Sn remaining without being alloyed is shown in
Tables 3 and 4 together with the amount of Ni and the amount of Sn
in each corrosion-resistant layer.
The corrosion-resistant layers formed on both surfaces of each
steel sheet are cathodically electrolyzed under conditions shown
in Tables 2 to 4 and then dried such that adhesive layers are
formed on the corrosion-resistant layers, whereby Surface-treated
Steel Sheet Nos. 1 to 31 shown in Tables 2 to 4 are prepared. The
adhesive layers of Surface-treated Steel Sheet Nos. 1, 16, 19, 22,
and 29 contain none of Co, Fe, Ni, V, Cu, Mn, and Zn and therefore
these sheets are comparative examples.
The amount of Ti in each adhesive layers is determined by X-
ray fluorescence spectrometry in comparison with a calibration
sheet in which the amount of each deposited metal is determined by
chemical analysis in advance. The amount of deposited Co, Fe, Ni,
V, Cu, Mn, and Zn is determined by a technique selected from the
group consisting of the same X-ray fluorescence spectrometry as
that used to determine the amount of Ti, chemical analysis, Auger
electron spectroscopy, and secondary ion mass spectrometry. The
mass ratio of Co, Fe, Ni, V, Cu, Mn, and Zn to that of Ti in the
adhesive layer is then evaluated. The presence of O in each of
Surface-treated Steel Sheet Nos. 1 to 31 can be confirmed by XPS
surface analysis.
For some of the surface-treated steel sheets, the thickness of
each adhesive layer and the line density of bumps are measured in
such a manner that a thin film sample is prepared by processing a
cross-sectional surface of the layer using an FIB and a cross-
sectional profile of the sample is observed with a TEM. In this
operation, an evaluation region of the sample is determined by SEM
observation in advance, a protective layer is formed thereon, and
the thin film sample is prepared by processing the cross-sectional
surface using the FIB and Ga ions so as to have a thickness of
about 0.1 µm and is then observed with the TEM. In the present
invention, the FIB is obtained with SMI-3050 MS2 manufactured by
SII-NT and the TEM is JEM-2010F manufactured by JOEL Ltd.
A SEM image is obtained with a SEM that can measure the shape
of irregularities. In the present invention, a high-resolution SEM,
ERA-8800FE, manufactured by Elionix Inc. is used. This instrument
includes four secondary electron detectors and can display an
image in which a difference in composition is emphasized or an
image which shows irregularities viewed in a specific direction
from sum signals and/or difference signals of secondary electrons.
The adhesive layers of some of the surface-treated steel sheets
are calculated for Rq, Ra, Rsk, and Rku on the basis of obtained
SEM images using an image-processing program attached to this
instrument. The area density of bumps is calculated in such a
manner that the SEM image obtained with the SEM is analyzed using
a three-dimensional surface analyzing program, "SUMMIT", developed
by Yanagi laboratory in Nagaoka University of Technology. Au is
vapor-deposited on each sample to a thickness of about 10 nm in
advance of observation. The resulting sample is observed with the
SEM at a magnification of 20000 times and an acceleration voltage
of 5 kV. The sample is analyzed in arbitrary five fields of view
and the obtained data is averaged, whereby the area density of the
bumps and the like are determined. For the calculation of Rq, Ra,
Rsk, and Rku, 100 or more cross-sectional curves are taken in each
field of view and evaluation values are obtained by averaging
values determined by evaluating roughness curves extracted' from
the cross-sectional curves and then averaged in five fields of
view.
Films which are made of polyethylene terephthalate
copolymerized with isophthalic acid and which have the following
properties are prepared: a draw ratio of 3.1 x 3.1, a thickness of
25 µm, a copolymerization ratio of 12 mole percent, and a melting
point of 224°C. The films are laminated on both surfaces of each
of Surface-treated Steel Sheet Nos. 1 to 31 such that the degree
of biaxial orientation (BO value) of the films is 150 under the
following lamination conditions: a steel sheet feed rate of 40
m/min, a nip length of 17 mm, and a time lag between pressing and
water cooling of one second. This allows Laminated Steel Sheet Nos.
1 to 31 to be prepared. The term "nip length" means the length of
a contact portion of a rubber roller with each steel sheet in the
feed direction of the steel sheet. Laminated Steel Sheet Nos. 1 to
31 are evaluated for wet resin adhesion as described below.
Wet resin adhesion: Humid resin adhesion is evaluated by a 180°
peeling test in a retort atmosphere having a temperature of 130°C
and a relative humidity of 100%. The 180° peeling test is a film-
stripping test in which a test piece (a size of 30 mm x 100 mm,
the front and rear surfaces being each n = 1, each laminated steel
sheet being n = 2) that includes a steel sheet 1 having a notched
portion 3 and a film 2 attached thereto as shown in Fig. 6A is
used, a weight 4 (100 g) is attached to an end of the test piece,
and the test piece is folded 180° over the film 2 as shown in Fig.
6B and then left for 30 minutes. A strip length 5 shown in Fig. 6C
is measured and then evaluated. The strip lengths (n = 2) of the
front and rear surfaces of each laminated steel sheet are averaged.
The smaller the strip length 5, the better the wet resin adhesion.
When the strip length 5 is less than 10 mm, the test piece is
evaluated to be excellent in wet resin adhesion as targeted in the
present invention.
The evaluation results are shown in Tables 5 and 6. Laminated
Steel Sheet Nos. 2 to 15, 17, 18, 20, 21, and 23 to 28, which are
examples of the present invention, have excellent wet resin
adhesion. In contrast, Laminated Steel Sheet Nos. 1, 16, 19, 22,
and 29, which are comparative examples, have poor wet resin
adhesion.
Industrial Applicability
According to the present invention, a surface-treated
steel sheet which contains no Cr and which is excellent in
wet resin adhesion can be produced. The surface-treated
steel sheet according to the present invention can be used
as an alternative to a conventional tin-free steel sheet
with no problem and can be used for containers for storing
oils, organic solvents, or paints without being coated with
resin. If a resin-coated steel sheet produced by coating
the surface-treated steel sheet with resin is formed into
cans or can lids and the cans or can lids are exposed to a
retort atmosphere, no resin is peeled off.
WE CLAIM

1. A surface-treated steel sheet comprising an adhesive
layer which is disposed on at least one surface of the steel
sheet and which contains Ti and at least one selected from
the group consisting of Co, Fe, Ni, V, Cu, Mn, and Zn, the
ratio of the total amount of Co, Fe, Ni, V, Cu, Mn, and Zn
to the amount of Ti contained therein being 0.01 to ten on a
mass basis.
2. The surface-treated steel sheet according to Claim 1,
wherein the adhesive layer has a thickness of 20 to 800 nm
and also has bumps arranged with a line density of one or
more per µm, the thickness of the adhesive layer is defined
as the maximum height H from the lower surface of the
adhesive layer to the bumps in a cross-sectional profile of
the layer observed with a transmission electron microscope
(TEM), and the line density of the bumps is defined as the
number of the bumps per unit length, the number thereof
being determined on the assumption that one of the bumps is
present when one or more intersections of an upper-level
horizontal line and a profile curve are present between two
intersections of a lower-level horizontal line and the
profile curve, the upper- and lower-level horizontal lines
being ±10 nm apart from a center line located at a position
given by the formula (H + L) / 2, where L represents the
minimum height from the lower surface of the adhesive layer
to the bottom of a recessed portion.
3. The surface-treated steel sheet according to Claim 1,
wherein the adhesive layer has a thickness of 20 to 800 nm
and also has bumps arranged with an area density of 16 or
more per µm2 and the area density of the bumps of the
adhesive layer is defined as the number of the bumps that
are 0.005 µm higher than an average line of the bumps and
recessed portions, the average line being determined in such
a manner that a SEM image of the layer observed with a
scanning electron microscope (SEM) is three-dimensionally
analyzed and filtered at a cut-off wavelength of 1.0 µm.
4. The surface-treated steel sheet according to Claim 3,
wherein the ratio (Rq / Ra) of root-mean-square roughness
(Rq) to arithmetic average roughness (Ra) is 1.3 or less,
the root-mean-square roughness and the arithmetic average
roughness being specified in JIS B 0601: 2201 and being
determined in such a manner that a cross-sectional curve is
derived from three-dimensional data obtained with a SEM and
then filtered at a cut-off wavelength of 1.0 µm.
5. The surface-treated steel sheet according to Claim 3 or
4, wherein skewness (Rsk) is 0.6 or less or kurtosis (Rku)
is four or less, the skewness and the kurtosis being
specified in JIS B 0601: 2201 and being determined in such a
manner that a cross-sectional curve is derived from three-
dimensional data obtained with a SEM and then filtered at a
cut-off wavelength of 1.0 µm.
6. A surface-treated steel sheet comprising an adhesive
layer which is disposed on at least one surface of the steel
sheet, which has a thickness of 20 to 800 nm, and which
contains Ti, wherein the adhesive layer has bumps arranged
with a line density of one or more per µm, the thickness of
the adhesive layer is defined as the maximum height H from
the lower surface of the adhesive layer to the bumps in a
cross-sectional profile of the layer observed with a
transmission electron microscope (TEM), and the line density
of the bumps is defined as the number of the bumps per unit
length, the number thereof being determined on the
assumption that one of the bumps is present when one or more
intersections of an upper-level horizontal line and a
profile curve are present between two intersections of a
lower-level horizontal line and the profile curve, the
upper- and lower-level horizontal lines being +10 nm apart
from a center line located at a position given by the
formula (H + L) / 2, where L represents the minimum height
from the lower surface of the adhesive layer to the bottom
of a recessed portion.
7. A surface-treated steel sheet comprising an adhesive
layer which is disposed on at least one surface of the steel
sheet, which has a thickness of 20 to 800 nm, and which
contains Ti, wherein the adhesive layer has bumps arranged
with an area density of 16 or more per µm2 and the area
density of the bumps of the adhesive layer is defined as the
number of the bumps that are 0.005 urn higher than an average
line of the bumps and recessed portions, the average line
being determined in such a manner that a SEM image of the
layer observed with a scanning electron microscope (SEM) is
three-dimensionally analyzed and filtered at a cut-off
wavelength of 1.0 µm.
8. The surface-treated steel sheet according to Claim 7,
wherein the ratio (Rq / Ra) of root-mean-square roughness
(Rq) to arithmetic average roughness (Ra) is 1.3 or less,
the root-mean-square roughness and the arithmetic average
roughness being specified in JIS B 0601: 2201 and being
determined in such a manner that a cross-sectional curve is
derived from three-dimensional data obtained with a SEM and
then filtered at a cut-off wavelength of 1.0 µm.
9. The surface-treated steel sheet according to Claim 7 or
8, wherein skewness (Rsk) is 0.6 or less or kurtosis (Rku)
is four or less, the skewness and the kurtosis being
specified in JIS B 0601: 2201 and being determined in such a
manner that a cross-sectional curve is derived from three-
dimensional data obtained with a SEM and then filtered at a
cut-off wavelength of 1.0 µm.
10. The surface-treated steel sheet according to any one
of Claims 1 to 9, wherein the amount of Ti in the adhesive
layer is 3 to 200 mg/m2 per one surface.
11. The surface-treated steel sheet according to any one
of Claims 1 to 10, further comprising a corrosion-resistant
layer which is disposed on at least one surface of the steel
sheet; which includes at least one selected from the group
consisting of a Ni layer, a Sn layer, a Fe-Ni alloy layer, a
Fe-Sn alloy layer, and a Fe-Ni-Sn alloy layer; and which is
disposed under the adhesive layer.
12. The surface-treated steel sheet according to any one
of Claims 1 to 11, coated with resin.
13. A method for producing a surface-treated steel sheet,
comprising forming a corrosion-resistant layer, including at
least one selected from the group consisting of a Ni layer,
a Sn layer, a Fe-Ni alloy layer, a Fe-Sn alloy layer, and a
Fe-Ni-Sn alloy layer, on at least one surface of a steel
sheet and forming an adhesive layer in such a manner that
the resulting steel sheet is cathodically electrolyzed in an
aqueous solution containing ions of Ti and ions of at least
one selected from the group consisting of Co, Fe, Ni, V, Cu,
Mn, and Zn.
14. The surface-treated steel sheet-producing method
according to Claim 13, wherein the content of Ti in the
aqueous solution is 0.008 to 0.07 mol/1 and the molar ratio
of at least one selected from the group consisting of Co, Fe,
Ni, V, Cu, Mn, and Zn to Ti in the aqueous solution is 0.01
to 10.
15. The surface-treated steel sheet-producing method
according to Claim 13 or 14, wherein the amount of Ti in the
adhesive layer is 3 to 200 mg/m2 per one surface.

It is an object to provide a surface-treated steel sheet
which contains no Cr, which is excellent in wet resin
adhesion, and which can be used as an alternative to a
conventional tin-free steel sheet and to provide a resin-
coated steel sheet produced by coating the surface-treated
steel sheet with resin. A surface-treated steel sheet
including an adhesive layer which is disposed on at least
one surface of the steel sheet and which contains Ti and at
least one selected from the group consisting of Co, Fe, Ni,
V, Cu, Mn, and Zn, the ratio of the total amount of Co, Fe,
Ni, V, Cu, Mn, and Zn to the amount of Ti contained therein
being 0.01 to ten on a mass basis, and a method for
producing the surface-treated steel sheet.
A surface-treated steel sheet including an adhesive layer
which is disposed on at least one surface of the steel sheet,
which has a thickness of 20 to 800 nm, which contains Ti,
and which has bumps arranged with a line density of one or
more per μm. The thickness of the adhesive layer is defined
as the maximum height H from the lower surface of the
adhesive layer to the bumps in a cross-sectional profile of
the layer observed with a transmission electron microscope
(TEM) . The line density of the bumps is defined as the
number of the bumps per unit length, the number thereof
being determined on the assumption that one of the bumps is

Documents:

1469-KOLNP-2010-(11-09-2014)-CORRESPONDENCE.pdf

1469-KOLNP-2010-(11-09-2014)-FORM-1.pdf

1469-KOLNP-2010-(12-08-2014)-ABSTRACT.pdf

1469-KOLNP-2010-(12-08-2014)-AMANDED PAGES OF SPECIFICATION.pdf

1469-KOLNP-2010-(12-08-2014)-ANNEXURE TO FORM 3.pdf

1469-KOLNP-2010-(12-08-2014)-CLAIMS.pdf

1469-KOLNP-2010-(12-08-2014)-CORRESPONDENCE..pdf

1469-KOLNP-2010-(12-08-2014)-CORRESPONDENCE.pdf

1469-KOLNP-2010-(12-08-2014)-OTHERS.pdf

1469-KOLNP-2010-(12-08-2014)-PETITION UNDER RULE 137.pdf

1469-KOLNP-2010-(22-09-2014)-PETITION UNDER RULE 137.pdf

1469-kolnp-2010-abstract.pdf

1469-kolnp-2010-claims.pdf

1469-KOLNP-2010-CORRESPONDENCE-1.1.pdf

1469-kolnp-2010-correspondence.pdf

1469-kolnp-2010-description (complete).pdf

1469-kolnp-2010-drawings.pdf

1469-kolnp-2010-form 1.pdf

1469-KOLNP-2010-FORM 18.pdf

1469-kolnp-2010-form 2.pdf

1469-kolnp-2010-form 3.pdf

1469-kolnp-2010-form 5.pdf

1469-kolnp-2010-international publication.pdf

1469-kolnp-2010-international search report.pdf

1469-kolnp-2010-others.pdf

1469-KOLNP-2010-PA.pdf

1469-kolnp-2010-pct priority document notification.pdf

1469-kolnp-2010-pct request form.pdf

1469-kolnp-2010-specification.pdf

1469-kolnp-2010-translated copy of priority document.pdf

abstract-1469-kolnp-2010.jpg

« Previous Patent

Next Patent »

Patent Number

265620

Indian Patent Application Number

1469/KOLNP/2010

PG Journal Number

10/2015

Publication Date

06-Mar-2015

Grant Date

02-Mar-2015

Date of Filing

26-Apr-2010

Name of Patentee

JFE STEEL CORPORATION

Applicant Address

2-3, UCHISAIWAI-CHO 2-CHOME, CHIYODA-KU, TOKYO 100-0011 JAPAN

Inventors:

#	Inventor's Name	Inventor's Address
1	YUKA NISHIHARA	C/O INTELLECTUAL PROPERTY DEPARTMENT, JFE STEEL CORPORATION, 2-3 UCHISAIWAI-CHO 2-CHOME, CHIYODA-KU, TOKYO 100-0011, JAPAN
2	TAKESHI SUZUKI	C/O INTELLECTUAL PROPERTY DEPARTMENT, JFE STEEL CORPORATION, 2-3 UCHISAIWAI-CHO 2-CHOME, CHIYODA-KU, TOKYO 100-0011, JAPAN
3	NORIKO MAKIISHI	C/O INTELLECTUAL PROPERTY DEPARTMENT, JFE STEEL CORPORATION, 2-3 UCHISAIWAI-CHO 2-CHOME, CHIYODA-KU, TOKYO 100-0011, JAPAN
4	TAKUMI TANAKA	C/O INTELLECTUAL PROPERTY DEPARTMENT, JFE STEEL CORPORATION, 2-3 UCHISAIWAI-CHO 2-CHOME, CHIYODA-KU, TOKYO 100-0011, JAPAN
5	HIROKI IWASA	C/O INTELLECTUAL PROPERTY DEPARTMENT, JFE STEEL CORPORATION, 2-3 UCHISAIWAI-CHO 2-CHOME, CHIYODA-KU, TOKYO 100-0011, JAPAN
6	NORIHIKO NAKAMURA	C/O INTELLECTUAL PROPERTY DEPARTMENT, JFE STEEL CORPORATION, 2-3 UCHISAIWAI-CHO 2-CHOME, CHIYODA-KU, TOKYO 100-0011, JAPAN
7	KAORU SATO	C/O INTELLECTUAL PROPERTY DEPARTMENT, JFE STEEL CORPORATION, 2-3 UCHISAIWAI-CHO 2-CHOME, CHIYODA-KU, TOKYO 100-0011, JAPAN
8	TAKASHI KAWANO	C/O INTELLECTUAL PROPERTY DEPARTMENT, JFE STEEL CORPORATION, 2-3 UCHISAIWAI-CHO 2-CHOME, CHIYODA-KU, TOKYO 100-0011, JAPAN

PCT International Classification Number

C23C 28/00

PCT International Application Number

PCT/JP2008/070255

PCT International Filing date

2008-10-30

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	2007-282806	2007-10-31	Japan