JP5150916B2 - Pre-coated metal plate and manufacturing method thereof - Google Patents

Description

  The present invention relates to a pre-coated metal plate, a metal molded body obtained by molding the pre-coated metal plate, and a method for producing the pre-coated metal plate, in particular, for example, for home appliances, building materials, civil engineering, machinery, automobiles, furniture, The present invention relates to a pre-coated metal sheet having excellent design properties such as stain resistance and sharpness in applications such as containers.

  For example, a pre-coated metal plate coated with a pre-colored coating film is used in place of a post-painted product that has been painted after processing a conventional metal plate as an outer plate in the home appliance field, building material field, automobile field, etc. It has become like this. On the other hand, in these applications, there has been an increasing demand for painting with an excellent appearance of painting from the viewpoint of design and design.

  As a technique for improving the sharpness of a coating film, for example, a technique for reducing the surface roughness of a metal plate as a base material as described in Patent Document 1, a molecular weight as described in Patent Document 2 A technique for coating a coating film using a low-resin resin, and a technique for coating a clear coating film on a colored coating layer as disclosed in Patent Document 3, are disclosed.

  When producing a precoat metal plate industrially, as described in Non-Patent Document 1, it is manufactured in a continuous coating line called a coil coating line. In a normal coil coating line, a primer coating having a rust prevention function is applied onto a metal plate in a coating device called a roll coater or curtain coater, baked in a hot air oven or the like, and then colored again in the coating device. Two-time coating and two-time baking (generally referred to as a two-coat two-bake method) in which a paint is applied and baked are common. Therefore, even if an attempt was made to apply a clear paint or other coating film excellent in sharpness and design on the colored layer, it was necessary to invest a large amount of equipment and add more coating equipment and ovens. However, as a means for solving this problem, as described in Patent Documents 4 to 12, there is known a wet-on-wet coating method in which a paint is repeatedly applied in an undried state.

  On the other hand, pre-coated metal sheets are used after being molded after coating, so it is common to coat a flexible film with high elongation. On the other hand, such resins have poor barrier properties against contaminants. The disadvantage is that it is poor in stain resistance. In Patent Document 13, a polyester resin having a glass transition point of 5 to 40 ° C. and a number average molecular weight of 15,000 to 30,000 and a hexamethoxymethylolated melamine resin are blended in a mass ratio of 75/25 to 55/45. Painted metal plate having excellent red magic contamination and excellent workability, obtained by a paint comprising 1 to 2 parts by mass of an amine block of dodecylbenzenesulfonic acid per 100 parts by mass of the polyester-melamine resin prepared A coating composition is disclosed.

JP-A-7-150326 JP-A-1-304934 JP-A-10-66931 JP-A-11-19581 Japanese Patent Laid-Open No. 11-19582 JP-A-11-19583 Japanese Patent Laid-Open No. 11-19484 Japanese Patent Laid-Open No. 11-19585 Japanese Patent Laid-Open No. 11-19586 Japanese Patent Laid-Open No. 11-57608 JP-A-11-76932 JP-A-11-76933 JP-A-2-269168 Ueda et al., Coloring Materials, 72 (8), 525-531 (1999)

  The method of obtaining sharpness by controlling the surface roughness of the base material of the pre-coated metal sheet is relatively low as long as the surface roughness of the base metal sheet can be controlled, regardless of the coating film used. While high clarity can be obtained, the surface roughness of the base metal plate can be controlled by rolling the metal with a rolling roll with an adjusted surface roughness or polishing it with a polishing machine. There must be. Therefore, in order to produce a precoated metal plate excellent in sharpness by this method, there is a disadvantage that much labor and cost are required. On the other hand, the method of obtaining a pre-coated metal plate with excellent image clarity by applying a paint using a resin having a low molecular weight is compared with the method obtained by controlling the surface roughness of the base metal plate. However, since a specific resin must be used for the paint, it is difficult to impart other coating film performance such as processability.

  As a method for obtaining a pre-coated metal plate that is relatively easily excellent in sharpness, a method of coating a transparent clear coating on the colored coating layer is suitable. In addition, wet-on-wet coating is suitable for applying multiple layers of design coatings such as colored coating layers and clear coating layers on a general coil coating line after applying anti-corrosion coating. is there. However, when ordinary paint is simply wet-on-wet, the curing agent moves between the undried coating layers, the coating surface tends to shrink and cure, and fine wrinkles are generated on the coating surface after baking. However, there is a drawback that the sharpness and gloss are reduced, or that the surface of the coating film is greatly wrinkled and shrinks. In order to suppress this defect, the present inventors diligently studied and found that there is a method of suppressing curing shrinkage by reducing the amount of all cross-linking agents (curing agents) added to wet-on-wet coating. However, when the amount of the curing agent is decreased, the stain resistance of the coating film is poor and practical use is difficult.

  On the other hand, in order to improve the contamination resistance, the technique of Patent Document 13 is used to apply wet-on-wet coating with an acid catalyst neutralized with a volatile basic substance. Since the acid catalyst neutralized in the step floats on the surface of the coating film and the basic substance is dissociated on the surface of the coating film, the curing reaction in the vicinity of the coating film surface during baking is promoted. Therefore, the curing agent of the lower coating layer laminated by wet-on-wet diffuses to the upper layer beyond the layer, and further, the curing reaction near the surface layer is promoted, so that the curing shrinkage at the coating surface layer is reduced. It has become noticeable, and it has been found that there are defects that sharpness, gloss reduction and shrinkage appearance become severe due to fine wrinkles. Decreasing the addition amount of acid catalyst neutralized with volatile basic substances in the paint or the addition amount of curing agent suppresses curing shrinkage and improves sharpness and gloss, but reduces stain resistance. End up.

  Therefore, the present invention has been made in view of such problems. In a precoated metal plate obtained by wet-on-wet coating of a paint, a metal molded body obtained by forming the coating, and a method for producing a precoated metal plate, The purpose is to achieve both design properties such as projectivity and luster, and contamination resistance.

The present inventors diligently studied to solve the above-described problems, and found that the curing reaction when baking a wet-on-wet coating film can be controlled by the following method.
1) When multiple layers of melamine curable paint are laminated and wet-on-wet painted and baked, melamine is concentrated near the interface of each layer.
2) When only butylated melamine is applied to the curing agent of any layer of the multilayer coating film, and melamine other than butylated melamine is applied to the coating material of the other layer, these are wet-on-wet painted and baked. Since the melamine in the other coating layer diffuses to the layer to which the chlorinated melamine is applied, the melamine concentration of the entire layer to which the butylated melamine is applied becomes high.
3) Applying a paint with an acidic catalyst neutralized with a volatile basic substance to one or more layers of the multilayer coating, and applying these paints on a wet-on-wet and baking, volatilizes in any layer Even when an acidic catalyst neutralized with a basic basic substance is added, melamine is concentrated in the uppermost coating film of a multilayer coating film wet-on-wet, and fine wrinkles due to curing shrinkage are prominent.
4) Apply a paint using melamine other than butylated melamine as the curing agent to the upper layer of the multilayer coating film and adding an acidic catalyst neutralized with a volatile basic substance, and curing only the butylated melamine in the lower layer Applying the paint used as, when wet-on-wet coating and baking, melamine is particularly concentrated near the interface between the lower layer coating and the upper layer coating, the melamine concentration of the entire lower layer coating is increased, Furthermore, although the melamine concentration of the upper layer coating film is lowered as a whole, melamine is concentrated near the outermost surface. And it becomes difficult for a coating film to cure and shrink.

  The mechanism of the above phenomenon 1) is that the melamine curable paint is laminated in a wet state, so that the melamine in each layer passes through the layer interface and correlates with each other. I think. The driving force with which melamine moves relative to each other is considered to be a difference in melamine concentration due to the difference in the amount of melamine added in the paint of each layer, a difference in melamine reaction rate due to a difference in melamine type or catalyst type in each layer of paint.

  The mechanism of the occurrence of the phenomenon 2) is that butylated melamine has the highest self-condensability and reactivity among various types of melamine, so that butylated melamine itself diffuses to other layers. It thinks that it becomes difficult to diffuse in the paint because a self-condensation reaction occurs and forms self-condensed particles before moving. On the other hand, the self-condensation reaction of butylated melamine becomes driving force, and melamine other than unreacted butylated melamine contained in other layers moves to the layer to which butylated melamine is added, so butylated melamine is added. It is considered that the melamine concentration of the layer is increased.

  The occurrence mechanism of the phenomenon 3) is the same as the conventionally known mechanism. As the temperature of the volatile basic substance increases in the baking process, it floats on the surface layer of the coating film in an attempt to volatilize from within the coating film. Along with this, the acidic catalyst also floats on the surface of the coating film. Then, since a volatile basic substance dissociates in the coating film surface layer, it is considered that the catalyst is activated in the vicinity of the coating film surface layer and melamine is concentrated on the coating film surface layer. Even if the acid catalyst neutralized with a volatile basic substance is not added to the upper layer paint but added only to the lower layer paint, it is a volatile basic substance contained in the lower layer paint. Is moved to the uppermost coating film and activates the catalytic reaction in the uppermost coating film, so that melamine is concentrated in the uppermost coating film, and curing shrinkage is likely to occur.

  The occurrence mechanism of the phenomenon 4) is a combination of the findings 1) to 3). When wet-on-wet coating is applied, melamine is concentrated near the interface of the coating film. Since the self-condensation reaction occurs early in the curing reaction process, it becomes a driving force, and the melamine in the upper coating moves to the lower coating and concentrates in the lower coating to accelerate the curing reaction. The speed is reduced, and the generation of wrinkles due to curing shrinkage is suppressed. However, on the other hand, as the temperature of the paint rises in the baking process, the volatilization of the volatile basic substance in the upper paint is promoted, which becomes a driving force, and the curing reaction of melamine other than butylated melamine in the upper paint is the upper layer. It is promoted near the surface layer of the coating film, and melamine is concentrated near the surface layer.

The present invention has been completed based on such knowledge, and the gist of the present invention is as follows.
(1) A pre-coated metal plate having at least two multilayer coating layers on one or both sides of a metal plate, wherein the multilayer coating layer is a coating film formed on the outermost surface; An intermediate coating film layer that is a lower coating film in contact with the top coating layer, and the coating material forming the top coating layer contains only an aminoplast resin other than butylated melamine as a crosslinking agent, The coating material forming the coating layer contains only butylated melamine as a crosslinking agent, and the butylated melamine content of the coating material forming the intermediate coating film is 20 to 50 parts by mass with respect to 100 parts by mass of the binder resin solid content. And the nitrogen coating ratio defined by the following formula (I) obtained from the element concentration measurement result in the depth direction in the high frequency discharge type glow discharge optical emission spectrometry for the multilayer coating layer is N _c , and the top coating layer Surface in contact with air in the layer As zero point, the distance in the depth direction from the surface of the top coating layer T ([mu] m), said top coating layer and the intermediate coated film layer position of the interface T ₁ of the and _([mu] m), the intermediate coated film A pre-coated metal characterized by satisfying all of the following conditions (A), (B), and (E), where T ₂ (μm) is the position of the interface between the intermediate layer and the lower layer in contact with the intermediate coating film: Board.
(A) In [T ₁ −1.0] ≦ T ≦ “T ₁ +1.0”, N _c has a maximum value N _c-max .
(B) When the minimum value of _{N c} in the range of _{T 1} ≦ _T ≦ _{T 2} and _{N c-min,} a _{0.2 ≦ [N c-max -N} c-min] ≦ 1.0.
(E) N _c (outermost layer value N _c ) of the surface (T = 0) in contact with air of the top coating layer is 0.5 or more.
N _c = [N] / {[N] + [O] + [C]} (I)
Here, [N] is the spectral intensity of nitrogen, [O] is the spectral intensity of oxygen, and [C] is the spectral intensity of carbon.
(2) The precoated metal sheet according to (1), wherein the N _c-max is 0.5 or more.
(3) The pigment contained in the top coating layer or both the top coating layer and the intermediate coating layer is a red pigment, yellow pigment, orange pigment, metallic pigment, and pearl pigment. The precoated metal sheet according to (1) or (2), which is one or more selected from the group consisting of:
(4) The pre-coated metal sheet according to (1) or (2), wherein the top coating layer is a clear coating containing no pigment.
(5) The precoated metal sheet according to any one of (1) to (4), wherein the top coating layer has a —Si—O— bond in a resin skeleton that forms the coating.
(6) The aminoplast resin content of the coating material forming the top coating layer is 20 to 50 parts by mass with respect to 100 parts by mass of the binder resin solid content, and the coating material forming the top coating layer is volatilized. (1) to (5), characterized in that an acidic catalyst neutralized with a basic basic substance and the paint forming the intermediate coating film does not contain an acidic catalyst neutralized with a volatile basic substance. The precoated metal plate according to any one of the above.
(7) The precoated metal sheet according to any one of (1) to (6) is formed by one or more processes selected from bending, drawing, overhanging, punching, or shearing. A metal molded body.
(8) At least two layers of wet-on-wet coating or multi-layer simultaneous coating with a paint satisfying the following conditions (C), (D), (F), (G), (H) on one or both surfaces of a metal plate A method for producing a precoated metal sheet, characterized by performing multi-layer simultaneous baking.
(C) The coating material that forms the outermost top coating layer contains only an aminoplast resin other than butylated melamine as a crosslinking agent.
(D) coating composition forming the intermediate coated film in contact with said top coating layer, see contains only butylated melamine as a crosslinking agent, butylated melamine content of coating composition forming the intermediate coated film, a binder resin solids It is 20-50 mass parts with respect to 100 mass parts .
(F) The aminoplast resin content of the coating material forming the top coating layer is 20 to 50 parts by mass with respect to 100 parts by mass of the binder resin solid content.
(G) The coating material which forms the said top coating film layer contains the acidic catalyst neutralized with the volatile basic substance.
(H) The coating material forming the intermediate coating film does not contain an acidic catalyst neutralized with a volatile basic substance.
( 9 ) The manufacturing method of the precoat metal plate as described in (8 ) whose content of the said acidic catalyst is 0.1-1 mass part with respect to 100 mass parts of binder resin solid content.

  According to the present invention, it is possible to provide a pre-coated metal plate that is more excellent in design properties such as sharpness than before and is excellent in stain resistance. In particular, by overcoming the shortcomings of wet-on-wet coating, which has been expected to be capable of mass-producing pre-coated metal sheets with various design features and functions that can be applied in multiple layers more easily than before. It became possible to realize wet-on-wet coating in the pre-coated metal sheet industry. Therefore, it becomes easy to apply a pre-coated metal plate to parts that require design properties that could only be handled by post-coating so far, and using pre-coated metal plates has become a problem in post-coating. Not only can the problem of volatile organic solvents (VOC) be solved, but also cost reduction and factory space can be achieved by eliminating painting equipment by users. Therefore, it can be said that the present invention is an industrially extremely valuable invention.

  Exemplary embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

The present invention is a pre-coated metal plate having at least two or more multilayer coating layers on one side or both sides of a metal plate, wherein a top coating layer in contact with air is a top coating layer, and a lower layer in contact with the top coating layer The coating film is defined as an intermediate coating film layer, the element concentration distribution in the depth direction of the coating film is measured by high-frequency discharge glow discharge emission spectrometry (hereinafter referred to as high-frequency GDS), and the nitrogen intensity ratio N _c = [Spectral intensity of nitrogen] / {[Spectral intensity of nitrogen] + [Spectral intensity of oxygen] + [Spectral intensity of carbon]}, where the surface of the top coating layer in contact with air is zero When the distance in the depth direction is T, the depth of the interface between the top coating film and the intermediate coating film is T ₁ , and the depth of the interface between the intermediate coating film and the coating film under the intermediate coating film is T ₂ Contamination resistance and design satisfying both the following conditions (A) and (B) Excellent is a pre-coated metal plate.
(A) In [T ₁ −1.0 μm] ≦ T ≦ [T ₁ +1.0 μm], N _c has a maximum value N _c-max (B) N _c in the range of T ₁ ≦ T ≦ T ₂ When the minimum value is defined as N _c-min ,
0.2 ≦ [N _c−max −N _c−min ] ≦ 1.0

Here, the value of _Nc indicates the nitrogen concentration derived from the aminoplast resin used as the curing agent for the coating film, and is an index of the aminoplast resin concentration in the coating film. The melamine cross-linked coating film laminated by wet-on-wet has an aminoplast resin at [T ₁ -1.0 μm] ≦ T ≦ [T ₁ +1.0 μm] near the interface between the top coating film and the intermediate coating film. In order to concentrate, nitrogen concentration _Nc shows a maximum value. When the depth T from the surface layer of the coating film is T ≦ [T ₁ −1.0 μm] or T ≧ [T ₁ +1.0 μm], it cannot be regarded as the vicinity of the interface between the coating films. In the range of the specified interface, there is no maximum value. Multi-layer simultaneous coating or wet-on-wet coating technology in which aminoplast resin interlayer movement does not occur in the baking process and aminoplast resin interlayer movement occurs. It is not suitable because it cannot be assumed. Multi-layer simultaneous coating or non-wet-on-wet coating is not suitable because the baking process during coating increases. Moreover, it is not suitable because the adhesion between the coating layers at the interface is lowered.

The relationship between the minimum value N _c-min in the range of T ₁ ≦ T ≦ T ₂ (representing the range of the intermediate coating film) and the maximum value N _c-max near the interface is 0.2 ≦ [N _{c− max-} N _c-min ] ≦ 1.0, the aminoplast resin in the top coating film moves to the intermediate coating film below, and the aminoplast resin concentration in the intermediate coating film is high. Represents. [ _{Nc-max- Nc-min} ] ≧ 1.0 indicates that the aminoplast resin concentration of the intermediate coating film is low, and the amount of aminoplast resin transferred from the top coating film to the intermediate coating film is small. Is unsuitable. Further, in the range of [N _c-max −N _c-min ] ≦ 0.2, it indicates that the aminoplast resin is not concentrated near the interface. It is not suitable because it cannot be regarded as technology.

Further, when the value of N _c-max is 0.5 or more, the stain resistance, particularly the oil stain resistance is further improved, which is more preferable. The _{Nc at} T = 0, which is the surface in contact with air of the multilayer coating layer of the precoated metal sheet of the present invention, is 0.5 or more, so that the stain resistance, particularly the magic stain resistance, is good . Contaminants such as magic are only slightly adhered to the outermost surface layer of the coating film, and therefore, the magic stain resistance is improved only by increasing the aminoplast resin concentration in the vicinity of the outermost surface layer of the coating film. On the other hand, for oil stains, a large amount of oil mixed with contaminants adheres to the surface of the coating film, and after a long time, the contaminants penetrate into the coating film along with the oil. It is more preferable to increase the aminoplast resin concentration in the vicinity of the interface between the coating film and the intermediate coating film.

In order to control the nitrogen concentration of the coating film of the precoated metal sheet of the present invention as described above, the undercoating film is not applied on one side or both sides of the metal sheet or is applied and baked. In addition, two or more layers of paint satisfying both the following conditions (C) and (D) are wet-on-wet coated and simultaneously baked in multiple layers to diffuse the aminoplast resin in the top coating into the intermediate coating. This can be achieved by concentrating the aminoplast resin at the interface between the top coating layer and the intermediate coating layer and increasing the concentration of the aminoplast resin in the intermediate coating layer.
(C) The top layer of the top layer contains only an aminoplast resin other than butylated melamine as a crosslinking agent. (D) The intermediate coating under the top layer of the top layer contains only a butylated melamine resin as a crosslinking agent. The amount of butylated melamine added is 20 parts by mass or more with respect to 100 parts by mass of the binder resin solid content.

  When butylated melamine is used for the top coating, or when an aminoplast resin other than butylated melamine is used for the intermediate coating, the top coating laminated by wet-on-wetting is applied to the intermediate coating below it. Since aminoplast resin migration does not occur, sharpness and gloss are lowered, which is not suitable. Further, when the addition amount of butylated melamine contained in the intermediate coating is less than 20 parts by mass with respect to 100 parts by mass of the binder resin in the coating, from the top coating laminated by wet on wet to the intermediate coating below it This is unsuitable because the amount of aminoplast resin transferred becomes small and the sharpness and gloss deteriorate.

  The aminoplast resin other than butylated melamine used in the top coating film of the precoated metal sheet of the present invention is not particularly defined as long as it is other than butylated melamine, and is generally known melamine resin, for example, fully alkyl type Melamine resins such as methylated melamine, imino group methylated melamine, methylol melamine, methylol group methylated melamine, fully alkyl mixed etherified melamine, methylol group mixed etherified melamine, imino group mixed etherified melamine, A benzoguanamine resin, an amino resin, or the like can be used. Commercially available products such as Cymel (registered trademark) 300 series and Cymel (registered trademark) 200 series manufactured by Mitsui Cytec can be used. The butylated melamine used for the intermediate coating under the uppermost top coating of the precoated metal sheet of the present invention is not particularly defined, and is generally known butylated melamine, for example, fully alkyl butylated melamine, imino group type Butylated melamine and the like can be used. Commercially available products such as My Coat (registered trademark) 500 series manufactured by Mitsui Cytec Co., Ltd. and Super Becamine (registered trademark) J-830 manufactured by Dainippon Ink & Chemicals, Inc. can be used. The binder resin used for the top coating and the intermediate coating on the precoated metal sheet of the present invention is not particularly defined, and is generally known as a coating resin, for example, a polyester resin, an acrylic resin, a fluorine resin, an epoxy resin. Resin, urethane resin, etc. can be used. These may be commercially available. The molecular weight of the binder resin used for the top coating film and the intermediate coating film of the present invention is not particularly specified. When the molecular weight of the binder resin is low, the crosslink density is increased, so that the stain resistance, hardness, and sharpness are increased, but the processability may be lowered. On the other hand, when the molecular weight of the binder resin is high, the processability is enhanced, but there is a possibility that the stain resistance, hardness, and pencil hardness are lowered. When the binder resin is a polyester resin, the number average molecular weight is preferably 2,000 to 30,000. Further, the glass transition temperature (Tg) of the binder resin is not particularly specified, and can be appropriately selected as necessary. If the Tg of the binder resin is low, the workability is improved, but the hardness and stain resistance may be lowered. If the Tg is high, the hardness and stain resistance are increased, but the workability may be lowered. 0-80 degreeC is suitable for Tg at the time of using a polyester resin for a binder.

The addition amount of the aminoplast resin added to the top layer top coating film and the intermediate coating layer under the top coating metal plate of the present invention is the same as that of the top layer top coating film. min Ru 20-100 parts by der respect to 100 parts by mass. Furthermore , when the aminoplast resin addition amount in the intermediate coating film under the top coating film is 20 to 50 parts by mass with respect to 100 parts by mass of the binder resin solid content in the coating film, sharpness and stain resistance are improved. It can be compatible at a higher level and is more suitable. When aminoplast resins loading in intercoat coating of the top coating and beneath it is less than 20 parts by mass, since the contamination resistance may deteriorate, and the 20 parts by weight or less. When the aminoplast resin addition amount of the top coating is more than 100 parts by mass, or the aminoplast resin addition amount in the intermediate coating is more than 50 parts by mass, There is a risk of cracking.

The paint of the top layer of the present invention comprises an acidic catalyst is neutralized with a volatile basic substance, and, the intercoat composition under the top layer that contains no catalyst, top precoated metal sheet of the present invention In the vicinity of the interface between the coating film and the intermediate coating film, the nitrogen concentration N _c has a maximum value N _c-max , and the minimum value N _c-min of N _c in the range of the intermediate coating film layer and the N _c-max relationship between the _{0.2 ≦ [N c-max -N} c-min] ≦ 1.0 , and the and, _{since N c} of topcoat outermost surface (surface in contact with air) is 0.5 or more, image clarity and gloss resistance contamination Ru better than with higher.

When the top coating layer does not contain a volatile basic substance, it is difficult for the aminoplast resin to concentrate on the outermost surface of the top coating, and the _{Nc of the} outermost layer is less than 0.5. May decrease. On the other hand, if a catalyst is included in the paint of the intermediate coating film layer, the curing rate in the intermediate coating film layer is too high, and the correlation transfer of the aminoplast resin from the top coating layer to the intermediate coating layer may be difficult to proceed. In addition, the nitrogen concentration in the coating film depth direction is out of the range of 0.2 ≦ [N _c−max −N _c−min ] ≦ 1.0, and there is a possibility that the vividness and gloss may be lowered.

  In the top coating film of the present invention, or the pigment contained in both the top coating film layer and the intermediate coating film layer, any one of a red pigment, a yellow pigment, an orange pigment, a metallic pigment, and a pearl pigment, Alternatively, any one of a plurality of types is more preferable because it is excellent in sharpness and can exhibit high design properties. The red pigment, yellow pigment and orange pigment added to the top coating and the intermediate coating of the present invention can be generally used. A commercially available product may be used. For example, in the case of red pigments, inorganic red pigments such as cadmium red and silver vermilion, organic soluble azo red pigments such as carmine 6B, lake red C, and watching red, organic materials such as permanent red, lake red 4R, and naphthol red. Insoluble azo red pigments, condensed azo red pigments such as chromoftal red, etc., in the case of yellow pigments, inorganic yellow pigments such as yellow lead, yellow iron oxide, cadmium yellow, disazo yellow, monoazo yellow, In the case of organic yellow pigments such as condensed azo yellow and orange pigments, inorganic orange pigments such as molybdenum orange and organic orange pigments such as disazo orange and permanent orange can be used. As the metallic pigment added to the top coating film and the intermediate coating film of the present invention, generally known metallic pigments such as aluminum flakes, nickel flakes, stainless flake gold foils and the like can be used. Glass flakes or resin flakes deposited with a metal such as aluminum may be used. These may be commercially available. As the pearl pigment added to the top coating film and the intermediate coating film of the present invention, generally known ones such as mica, mica coated with a metal oxide such as titanium oxide and iron oxide, and the like can be used.

  When the top coating film of the present invention is a clear coating film containing no pigment, the sharpness of the coating film is improved, which is more preferable.

  The intermediate coating film of the present invention may contain a white pigment. As the white pigment used in the intermediate coating film, generally known titanium oxide-based white pigments can be used. Surface-modified titanium oxide may be used. For example, as commercially available titanium oxide, “Taipaque” manufactured by Ishihara Sangyo Co., Ltd., “TITANIX” manufactured by Takeka Co., Ltd., or the like can be used.

  When the top coating film of the present invention contains Si derived from alkoxysilane or a hydrolysis-condensation product of alkoxysilane as a —Si—O— bond present in the resin skeleton forming the coating film, the coating film surface becomes hydrophilic. Therefore, when the pre-coated metal plate of the present invention is used outdoors, it is more preferable because the deposits adhering to the surface of the coating film are easily washed away by rain or the like, and a raindrop pattern or the like is hardly attached. In addition, the raindrop pattern is dirt that adheres along the traces of rain lines when rain falls on the surface of the paint film and flows down the paint film surface. This is called rain streak pollution. In addition, the performance of this drooling resistant to contamination is generally referred to as dripping resistance. In general, adding an alkoxysilane compound or an alkoxysilane hydrolysis condensate to the coating makes the coating surface hydrophilic, and contaminants adhering to the coating surface can easily flow off due to rain, etc., improving raindrop contamination It is known to do this, and the technology is disclosed in WO94 / 06870. However, the conventional technique has a problem in that Si derived from an alkoxysilane compound is difficult to concentrate on the surface layer of the coating film, and the hydrophilic expression on the surface of the coating film is unstable. On the other hand, in JP-A No. 2005-288963, it has a surface layer having a component derived from a partially hydrolyzed condensate of alkoxysilane and alkoxysilane, a component derived from a polyester resin, and a component derived from a melamine resin. By controlling the abundance ratio of Si and N at the depth position, increasing the abundance ratio of Si at the outermost layer, and increasing the N concentration at the depth positions of 10 nm and 30 nm from the outermost layer, the contamination resistance and workability are improved. A compatible technique is disclosed. Japanese Patent Application Laid-Open No. 2005-288963 discloses that the method for controlling the abundance ratio of Si and N can be controlled by the addition amount of alkoxysilane, the addition amount of melamine, and the addition amount of a catalyst of sulfonic acids blocked with amines. Yes. However, in this technique, if the amount of the melamine resin added or the amount of the catalyst added is increased for the purpose of improving the stain resistance, the coating film tends to shrink and cure, resulting in a decrease in the sharpness. doing.

  When the alkoxysilane and the hydrolysis condensate of alkoxysilane are added to the top coating of the precoated metal sheet of the present invention, the melamine resin in the top coating is concentrated near the interface between the top coating and the intermediate coating, Since the interlayer movement into the intermediate coating film can suppress the curing shrinkage on the surface layer of the top coating film, it is preferable because it can have high definition. Furthermore, since Si derived from alkoxysilane is further concentrated by the surface layer of the coating film, it is more preferable because the raindrop resistance is further improved. Although the addition amount of the alkoxysilane of the present invention and the hydrolysis condensate of alkoxysilane is not particularly limited, it is preferably 3 to 100 parts by mass with respect to 100 parts by mass of the binder resin solid content in the top coating film. . The alkoxysilane added to the top coating film of the present invention is generally known, for example, tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, tetrabutoxysilane, methyltrimethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane. Ethyltriethoxysilane, dimethoxydiethoxysilane, dimethoxydipropoxysilane and the like can be used. Moreover, the hydrolysis condensate of these alkoxysilanes may be sufficient.

  If necessary, generally known additives such as waxes, leveling agents, antifoaming agents, ultraviolet absorbers and the like can be added to the paint to be applied to the precoated metal sheet of the present invention.

  The precoated metal sheet of the present invention can be produced by applying a multilayer coating film including a top coating film and an intermediate coating film by simultaneous multilayer coating or wet-on-wet coating. Multi-layer simultaneous application is a method in which a plurality of layers of coating liquid are applied to a substrate in a state of being laminated simultaneously using a slot die coater or a slide hopper type curtain coater, and then dried and baked simultaneously in multiple layers. In addition, wet-on-wet coating means that after coating the coating liquid on the substrate once, another coating liquid is further coated on it in the wet state before the coating liquid dries. The multi-layer coating liquid is simultaneously dried and baked. For example, the lower layer coating film is applied with a roll coater or a curtain flow coater, and the upper layer coating film is applied with a coating method such as a curtain flow coater before baking this. Later, a multilayer coating film of a lower layer coating film and an upper layer coating film is baked simultaneously. The multi-layer simultaneous coating of the present invention, or a method of simultaneously baking a wet-on-wet coating film, is a commonly known coating baking furnace, for example, a hot air drying furnace, an induction heating furnace, an infrared heating furnace, or a combination thereof. A furnace or the like can be used.

  The precoat metal plate of the present invention can be coated with a primer coating film having a rust preventive paint function, if necessary. When the primer coating is applied, the corrosion resistance of the metal plate is improved, which is more preferable. As the primer coating film to be applied to the pre-coated metal plate of the present invention, generally known primer coating films for pre-coated metal plates, for example, polyester-based primers, epoxy-based primers, urethane-based primers and the like can be used. The curing agent for the primer coating film may be either melamine type or isocyanate type. As the rust preventive pigment to be added to the primer coating, generally known pigments such as chromate, phosphoric acid and silica can be used, but those other than chromate are more suitable because they are more environmentally friendly. is there. The primer coating film to be applied to the pre-coated metal plate of the present invention is generally applied by a known coating method such as a roll coater, roller curtain coater, ringer roll coater, spray coating, etc. For example, it can be baked in a hot air drying furnace, an induction heating furnace, an infrared heating furnace, or a furnace using these in combination.

  For the metal plate used in the present invention, generally known metal materials can be used. The metal material may be an alloy material. For example, a steel plate, a stainless steel plate, an aluminum plate, an aluminum alloy plate, a titanium plate, a copper plate, etc. are mentioned. The surface of these materials may be plated. Examples of the plating include zinc plating, aluminum plating, copper plating, nickel plating, and the like, and may be alloy plating thereof. In the case of steel plates, generally known steel plates and plated steel plates such as hot dip galvanized steel plates, electrogalvanized steel plates, zinc-nickel alloy plated steel plates, hot galvannealed steel plates, aluminum plated steel plates, aluminum-zinc alloyed steel plates, etc. Applicable.

  If the surface of the metal plate used in the present invention is generally subjected to a known chemical conversion treatment, the adhesion between the metal plate and the coating layer is improved, which is more preferable. As the chemical conversion treatment, zinc phosphate chemical conversion treatment, coating chromate treatment, electrolytic chromic acid treatment, reaction chromate treatment, chromate-free chemical conversion treatment, or the like can be used. As the chromate-free chemical conversion treatment, those treated with an aqueous solution containing a silane coupling agent, a zirconium compound, a titanium compound, tannin or tannic acid, a resin, silica and the like are known, and Japanese Patent Laid-Open No. 53-9238 is known. JP-A-9-241576, JP-A-2001-89868, JP-A-2001-316845, JP-A-2002-60959, JP-A-2002-38280, JP-A-2002-266081, You may use the well-known technique described in Kaikai 2003-253464 etc. These chemical conversion treatments are commercially available, for example, chromate treatment “ZM-1300AN” manufactured by Nihon Parkerizing Co., Ltd., chromate-free chemical conversion treatment “CT-E300N” manufactured by Nihon Parkerizing Co., Ltd., and trivalent chromium-based chemical conversion manufactured by Nippon Paint Co., Ltd. The treatment “Surfcoat (registered trademark) NRC1000” or the like can be used.

[Example-1]
Hereinafter, the details of the experiment of Example-1 will be described.
First, the details of the top paint used in the experiment of Example-1 will be described.

  “Byron (registered trademark) 63CS” (Tg: 7 ° C., number average molecular weight: 20000, hereinafter referred to as low Tg polyester), “Byron (registered trademark) GK140” (Tg), which is an amorphous polyester resin manufactured by Toyobo Co., Ltd. : 20 ° C., number average molecular weight: 14000, hereinafter referred to as medium Tg polyester), “Byron (registered trademark) 270” (Tg: 67 ° C., number average molecular weight: 23000, hereinafter referred to as high Tg polyester), Asahi Glass Co., Ltd. “LUMIFLON (registered trademark) LF552” (Tg: 20 ° C., number average molecular weight 12000, hereinafter referred to as fluorine) which is a fluorine-based resin manufactured by Nippon Shokubai Co., Ltd. A clear paint was prepared by adding a cross-linking agent and a catalyst to the acrylic. The melamine resin added as a cross-linking agent is “Cymel (registered trademark) 303” which is a fully alkyl methylated melamine resin (hereinafter referred to as methylated melamine) manufactured by Mitsui Cytec Co., Ltd., and an imino group methyl produced by Mitsui Cytec Co., Ltd. "Cymel (registered trademark) 325" which is a melamine fluoride (hereinafter referred to as imino group type melamine), and "Super Becamine" which is a butylated melamine resin (hereinafter referred to as butylated melamine) manufactured by Dainippon Ink & Chemicals, Inc. (Registered trademark) J830 "was used. The catalyst is “Catalyst 600” (hereinafter referred to as “strongly acidic catalyst”), which is a strong acid catalyst (type that is not neutralized with a volatile basic substance) manufactured by Mitsui Cytec, and a volatile base manufactured by Mitsui Cytec. "Catalyst 602" (hereinafter referred to as an amine neutralized strong acid catalyst) that is neutralized with a reactive substance, "Catalyst 296-9" (hereinafter referred to as a weakly acidic catalyst) that is a weakly acidic catalyst manufactured by Mitsui Cytec Used). Since “Byron (registered trademark) GK140”, “Byron (registered trademark) 270”, and “Alloset (registered trademark) 5535” are pellets or flakes, these are organic solvents (cyclohexanone by mass ratio: Solvesso 150). = Used in a mixture of 1: 1).

  Next, if necessary, the pigment added to the total resin solid content in the clear paint by adding “Taipek (registered trademark) CR-95”, which is titanium oxide made by Ishihara Sangyo Co., Ltd., to 50% by mass as necessary. A white paint with the corresponding amount added was also made. In this experiment, the clear paint was used as the top paint and the white paint was used as the intermediate paint.

  Details of the prepared top paint and intermediate paint are shown in Table 1 and Table 2, respectively.

  Also, a clear paint of FL641EU primer, which is a polyester primer for PCM manufactured by Japan Fine Coatings Co., Ltd., was prepared, and K-WHITE # 105 with tripolyaluminum dihydrogen phosphate manufactured by Teika, which is a chromate-free rust preventive pigment. Was added to 30 parts by mass with respect to 100 parts by mass of the solid content of the clear coating material to prepare a chromate-free primer.

  Hereinafter, the details of the precoated metal plate used in the experiment of Example-1 will be described.

Hot-dip galvanized steel sheet "Silver Zinc" (hereinafter referred to as GI) manufactured by Nippon Steel Corporation, zinc-nickel alloy-plated steel sheet "Zinclite" (hereinafter referred to as ZL) manufactured by Nippon Steel Corporation An electrogalvanized steel sheet “JINCOAT” (hereinafter referred to as EG) manufactured by Nippon Steel Corp. was prepared as an original plate. A plate thickness of 0.6 mm was used. The ZL plating adhesion used in this experiment was 20 g / m ^{2 on} one side, and the nickel content in the plating layer was 12%. The GI plating adhesion amount was 60 mg / m ² on one side, and the EG plating adhesion amount was 20 g / m ² on one side.

Next, the prepared original plate is spray-degreased with a 2% by weight, 50 ° C. aqueous solution of an alkaline degreasing solution “FC-4336” manufactured by Nihon Parkerizing Co., Ltd., washed with water, dried, and then chromate-free formed by Nihon Parkerizing Co., Ltd. The treatment “CT-E300N” was applied with a roll coater and dried in a hot air oven. The drying conditions in the hot air oven were 60 ° C. at the ultimate plate temperature of the steel plate. The coating amount of the chromate-free treatment was applied so that the total solid content was 200 g / m ² .

  Next, paint the primer coating on one side of the chemical-treated metal plate, and apply the gray color of “FL100HQ”, a back coating made by Nippon Fine Coatings, on the other side with a roll coater. Then, it was dried and hardened under the condition that the ultimate plate temperature of the metal plate was 210 ° C. in an induction heating furnace into which hot air was blown. And after dry baking, water was wiped with a spray to the painted metal plate, and water-cooled.

  Next, on the primer coating, intermediate coating and top coating are simultaneously laminated in a slide hopper type curtain coater, and the ultimate temperature of the metal plate is 230 ° C in an induction heating furnace blown with hot air. Under these conditions, the laminated coating films were simultaneously dried and cured. Then, after drying and baking, water was sprayed onto the coated metal plate and water-cooled to prepare a three-layer pre-coated metal plate (hereinafter, this coating method is referred to as “3C2B” coating).

  In addition, if necessary, only the intermediate coating was applied by the same method (no top coating was applied), and a two-layer pre-coated metal plate that was dried and cured was also produced (hereinafter, this coating method is referred to as “2C2B”). ).

  If necessary, apply only one layer of intermediate coating on the primer coating with a roll coater, and after baking as described above, apply one layer of top coating again on the coating with a roll coater. A baked three-layer pre-coated metal plate was also produced (the coating method in this procedure is referred to as “3C3B coating”).

  About each coating-film thickness of the produced precoat steel plate, the surface undercoat film was 5 micrometers in dry film thickness, the intermediate-coat film was 15 micrometers, and the topcoat film was 10 micrometers. The film thickness of the back coating was 5 μm in terms of dry film thickness. These film thicknesses can be adjusted by adjusting the rotational peripheral speed of the roll and the pressure between the rolls and the paint viscosity in the case of a roll coater, and the paint application pressure and paint viscosity in the case of a slide hopper type curtain coater. Controlled. Each film thickness was measured with an electromagnetic film thickness meter “LE-200J” manufactured by KET.

  Hereinafter, the details of the evaluation method of the precoated metal sheet produced in Experiment-1 will be described.

1. Coating film analysis by high-frequency GDS Using System 3860 manufactured by Rigaku Denki Kogyo Co., Ltd., discharge power of 30 W, argon flow rate of 250 ml / min. The spectral intensities of carbon and silicon were measured. Then, N _c = [nitrogen spectral intensity] / {[nitrogen spectral intensity] + [oxygen spectral intensity] + [carbon spectral intensity]} at each sampling time is calculated, and sampling time t and N _c are calculated. A graph showing the relationship was created. Next, using the spectrum of titanium present in the intermediate coating film as an index, the sampling time t during which the silicon spectral intensity greatly increased is determined as the interface T between the top coating film and the intermediate coating film. _The sampling time t corresponding to this interface was set to a depth T = 10 μm from the surface (because the film thickness of the top coating of the precoated metal plate prepared in this experiment was 10 μm). Further, the time t spectrum intensity decreased greatly titanium and interface T ₂ of the the intermediate coated film and the primer coating, the sampling time t corresponding to the interface and the depth T = 25 [mu] m from the surface (in this experiment Since the film thickness of the top coating film of the prepared pre-coated metal plate is 10 μm and the film thickness of the intermediate coating film is 15 μm). And since the relationship between the depth T from the coating film surface and the GDS sampling time t is directly proportional, a graph showing the relationship between the distance T in the depth direction from the surface of the top coating film and _Nc is created. did.

Then, from this graph, the maximum value of _{T 1 -1.0μm ≦ T ≦ T 1} + 1.0μm range _{(hereinafter,} referred to as _{N c-max} range) of _{N c} was investigated whether there to. The case where it was present in the range of T ₁ −1.0 μm ≦ T ≦ T ₁ +1.0 μm was evaluated as ◯, and the case where it was not present in the range was evaluated as ×.

Next, _{T 1} ≦ _T ≦ _T value of minimum values _{N c-min} of _{N c} in the range of _{2 (hereinafter,} referred to as _{N c-min} values) _{0.2 ≦ [N c-max -N} c-min ] ≦ 1.0, whether or not N _c-min is in the range of 0.2 ≦ [N _c-max −N _c-min ] ≦ 1.0, When it was outside this range, it was evaluated as x.

Next, the value of _Nc-max (hereinafter referred to as _Nc-max value) was investigated, and when this value was 0.5 or more, it was evaluated as ◯, and when it was less than 0.5, it was evaluated as x.

2. Measurement of sharpness of pre-coated metal plate The Gd value was measured with a portable sharpness gloss meter “PGD” (manufactured by Tokyo Kodenshi) for the sharpness of the coating film on the surface of the prepared pre-coated metal plate.

3. Gloss measurement of pre-coated metal plate JIS. K. According to 5600.4.7, the specular glossiness of the surface of the prepared precoated metal sheet was measured. The measurement conditions were an incident angle and a light receiving angle of 20 °.

4). Coating Film Workability Test The prepared precoated metal plate was bent 180 ° (adhesion bending), and the coating film in the processed part was visually observed to check for cracks in the coating film. When the 180 ° bending was performed, the pre-coated metal plate was bent so that the surface of the pre-coated metal plate was outside the bending, and the contact bending was performed (generally known as 0T bending). Then, the processed part is observed with a magnifying glass 10 times, ○ when there is no cracking or peeling of the coating film, △ when there are slight cracking or peeling in the coating film, clear large cracking or peeling off the coating film Some cases were evaluated as x. In addition, a processed part adhesion test is also conducted in which the tape is attached to the processed part and peeled off, and the adhesiveness after the tape is peeled is visually observed. The case where coating film peeling was observed was evaluated as Δ, and the case where the processing part front surface was peeling off was evaluated as x.

5. Magic Contamination Test After applying the magic ink black made by Teranishi Kagaku Co. to the coating surface of the pre-coated metal plate and leaving it to stand at room temperature for 24 hours, traces after wiping off the magic ink applied with ethanol Evaluated. The case where the magic mark disappeared and was not visible was evaluated as ◯, the case where the magic mark remained slightly was evaluated as △, and the case where the magic mark did not disappear was evaluated as ×.

6). Oil Contamination A solution obtained by adding 20% by mass of commercially available carbon black as a contaminant to “G-6216FS” manufactured by Nippon Kogyo Co., Ltd., which is a volatile lubricant, was applied to the surface of the coating film. It was allowed to stand in an atmosphere at 24 ° C. for 24 hours. The appearance of the coating film after visually wiping the coating film surface with ethanol was visually observed. And the case where the black contaminant was not adhering was evaluated as (circle), and the case where the coating-film surface layer was contaminated black was evaluated as x.

  Details of the evaluation results will be described below.

  Table 3 shows the precoated metal sheets prepared in the present invention and the evaluation results.

Precoated metal sheet of the present invention (Example 1,8～10, the present invention Example - 2 ~ 7,11～ 24) may be painted with a multilayer simultaneous coating excellent in sharpness, and excellent stain Had sex. When the amount of aminoplast resin added in the top coating is less than 20 parts by mass with respect to 100 parts by mass of the binder resin ( Reference Example-1), the _Nc value of the outermost layer is less than 0.5, and the magic contamination property Since the N _c-max value also becomes 0.5 or less and the oil contamination tends to decrease, the amount of aminoplast resin added is 20 parts by mass with respect to 100 parts by mass of the binder resin. The above is more preferable. Aminoplast resin addition amount in the top coating film is more than 100 parts by mass with respect to 100 parts by mass of binder resin (Example 7 of the present invention) because the processability tends to decrease. Is more preferably 70 parts by mass or less with respect to 100 parts by mass of the binder resin. In the top coating film, those using a catalyst that is not neutralized with a volatile basic substance ( Reference Examples-8 and 9) or those not containing a catalyst (Reference Example-10) are N _{c on} the outermost layer. Since the value is less than 0.5 and the magic contamination tends to decrease, it is more preferable to add a catalyst neutralized with a volatile basic substance to the top coating film. The amount of aminoplast resin added in the intermediate coating film exceeds 50 parts by weight with respect to 100 parts by weight of the binder resin (Example 17 of the present invention). Is more preferably 50 parts by mass or less with respect to 100 parts by mass of the binder resin. In addition, when the amount of aminoplast resin added in the intermediate coating film is less than 20 parts by mass with respect to 100 parts by mass of the binder resin (Comparative Example-25), the N _c-min value is below the specified range and the sharpness is poor. In addition, the N _c-max value is also less than 0.5 and the oil contamination is poor, which is not suitable.

Those using an aminoplast resin other than butylated melamine in the intermediate coating film of the pre-coated metal plate (Comparative Examples -26 to 32) have a N _c-min value outside the specified range of the present invention, resulting in poor visibility. Unsuitable.

The one using butylated melamine as the top coating film of the pre-coated metal plate (Comparative Example-33) is not suitable because the _Nc-min value falls outside the range defined in the present invention and the sharpness is poor.

The pre-coated metal sheet top coating and intermediate coating coated in each layer and baked with 3C3B (Comparative Example -34) has no _Nc maximum near the interface, and also has good work adhesion Because it is inferior, it is unsuitable.

[Example-2]
Hereinafter, the details of the experiment of Example-2 will be described.
First, the details of each paint used in the experiment of Example-2 will be described.

In the clear paint of “Top-3” prepared in Example-1, “Taipaque (registered trademark) CR-95”, which is titanium oxide manufactured by Ishihara Sangyo Co., Ltd., is used as a white pigment. 100 parts by weight (corresponding to 50% by weight in the coating film) was added to the mixture, and the mixture was stirred with a paint shaker to prepare a white paint. Similarly, the top paint is prepared by adding red, yellow and orange color pigments, metallic pigments and pearl-like pigments to the “top-3” clear paint prepared in the experiment of Example-1. Produced. Furthermore, an intermediate coating material was also prepared in which the white pigment of “intermediate coating material-2” prepared in Example-1 was changed to another pigment. Commercially available naphthol red for red pigments, commercially available disazo yellow for yellow pigments, commercially available disazopyrazolone orange for orange pigments, and aluminum, a commercially available metallic pigment for paints, for metallic pigments Flakes were used, and mica, which is a commercially available pearl pigment for paints, was used as the pearl pigment. As the primer paint, the same primer as that prepared in Example-1 was used.
Details of the prepared top paint and intermediate paint are shown in Tables 4 and 5, respectively.

Hereinafter, the details of the precoated metal plate used in the experiment of Example-2 will be described.
A precoated metal plate was prepared in the same manner as in Example-1.

Hereinafter, the details of the evaluation method of the precoated metal sheet produced in Example-2 will be described.
Evaluation of 1-5 described in Example-1 was implemented. In addition, the appearance was visually evaluated.

  Hereafter, the detail and evaluation result of the precoat metal plate created in Example-2 are described.

  The pigment contained in the top coating layer of the precoated metal sheet of the present invention or both the top coating layer and the intermediate coating layer is a red pigment, yellow pigment, orange pigment, metallic pigment, pearl tone. It is more preferable that the pigment is added (Examples 35 to 40 of the present invention) because it is excellent in design as well as sharpness.

  Invention Example-35 in which a red pigment is added to the top coating film is suitable because it has a bright red and high-definition appearance. Invention Example-36 to which a yellow pigment is added has a bright yellow and highly visible visual appearance, and is suitable. Invention Example 37, to which an orange pigment is added, has a vivid orange color and a highly visible visual appearance, and is suitable. Inventive Examples -38 and 39, to which metallic pigments and pearl pigments are added, are suitable because they have a metallic and pearly appearance with high brightness and a high-quality visual appearance.

  Inventive Example-40, in which a metallic pigment is added to the intermediate coating film and a pearl pigment is added to the top coating film, has a great luminance and has a visual appearance excellent in sharpness. Is more preferable. Invention Example-41 containing a red pigment in the intermediate coating film and also containing a red pigment in the top coating film has a deep and vivid visual appearance, and is more preferable.

[Example-3]
Hereinafter, the details of the experiment of Example-3 will be described.
First, the details of each paint used in the experiment of Example-3 will be described.

  “Byron (registered trademark) GK150” (Tg: 20 ° C., number average molecular weight: 14000, hereinafter referred to as medium Tg polyester-2), an amorphous polyester resin manufactured by Toyobo Co., Ltd., a crosslinking agent and a catalyst were added. A clear paint was created. A paint was prepared by adding tetramethoxysilane to the clear paint prepared. Moreover, Ishihara Sangyo Co., Ltd. titanium oxide "Taipeku (trademark) CR-95" was added as needed. Further, in this experiment, “intermediate coating-2” and “intermediate coating-12” created in Example-1 were used as intermediate coating materials, and the same primers as those prepared in Example-1 were used as primer coating materials.

  Details of the paints prepared are listed in Table 7.

Hereinafter, the details of the precoated metal plate used in the experiment of Example-3 will be described.
A precoated metal plate was prepared in the same manner as in Example-1. Furthermore, in this experiment, the primer paint was applied with a roll coater and baked at an ultimate plate temperature of 210 ° C in an induction heating furnace in which hot air was blown, and then only the top paint was applied with a roll coater, A sample of twice-baked twice-baked (hereinafter referred to as 2C2B), which was baked at an ultimate plate temperature of 230 ° C. in a blown induction heating furnace, was also produced.

Hereinafter, the details of the evaluation method of the precoated metal sheet produced in Example-3 are described.
In addition to the evaluations 1 to 5 described in Example 1, the following raindrop contamination evaluation was performed.

7). Raindrop pollution The prepared samples were subjected to an exposure test for 3 months at an outdoor exposure test site near the coast of Futtsu City, Chiba Prefecture. For the samples after the test, the presence or absence of raindrops was evaluated visually, ○ when there was no raindrops, △ when raindrops were observed slightly, and × when raindrops were clearly observed. evaluated.

  Hereinafter, the details and evaluation results of the precoated metal sheet produced in Example-3 are described.

  The evaluation results are shown in Table 8. When Si derived from alkoxysilane or a hydrolysis condensate of alkoxysilane is included in the top coating film of the precoated metal sheet of the present invention (Invention Example -42 to 48), this is not included (Invention Example-49) ) And more suitable for raindrop contamination. Moreover, the high definition and high gloss which were not able to be achieved by the conventionally known 2C2B coating (Comparative Examples-50 to 63) can be obtained, which is more preferable. In addition, the precoated metal sheet of the present invention is also compared with the case where a conventional coating material for a precoated metal sheet, for example, a coating material using melamine other than butylated melamine is applied to the intermediate coating (Comparative Example -64). The plate has high definition and high gloss and is suitable.

  As mentioned above, although preferred embodiment of this invention was described referring an accompanying drawing, it cannot be overemphasized that this invention is not limited to this example. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope of the claims, and these are naturally within the technical scope of the present invention. Understood.

It is explanatory drawing which shows the structural example of the precoat metal plate of this invention. It is a graph showing the example of the relationship between the coating-film depth and nitrogen concentration _Nc when the coating film of the precoat metal plate of this invention carries out the high frequency GDS analysis.

Claims (9)

A pre-coated metal plate having at least two multilayer coating layers on one side or both sides of the metal plate,
The multilayer coating layer has a top coating layer that is a coating formed on the outermost surface, and an intermediate coating layer that is a lower layer coating in contact with the top coating layer,
The coating film forming the top coating layer contains only an aminoplast resin other than butylated melamine as a crosslinking agent, and the coating material forming the intermediate coating layer contains only butylated melamine as a crosslinking agent,
The butylated melamine content of the paint forming the intermediate coating film is 20 to 50 parts by mass with respect to 100 parts by mass of the binder resin solid content,
The multilayer coating layer has a nitrogen intensity ratio defined by the following formula (I) obtained from the element concentration measurement result in the depth direction in high-frequency discharge glow discharge optical emission spectrometry, _Nc , and the air of the top coating layer With the surface in contact with the zero point, the distance in the depth direction from the surface of the top coating layer is T (μm), the position of the interface between the top coating layer and the intermediate coating layer is T ₁ (μm), When the position of the interface between the intermediate coating film and the lower layer in contact with the intermediate coating film is T ₂ (μm), all the following conditions (A), (B), and (E) are satisfied. Pre-coated metal plate.
(A) In [T ₁ −1.0] ≦ T ≦ “T ₁ +1.0”, N _c has a maximum value N _c-max .
(B) When the minimum value of _{N c} in the range of _{T 1} ≦ _T ≦ _{T 2} and _{N c-min,} a _{0.2 ≦ [N c-max -N} c-min] ≦ 1.0.
(E) N _c (outermost layer value N _c ) of the surface (T = 0) in contact with air of the top coating layer is 0.5 or more.
N _c = [N] / {[N] + [O] + [C]} (I)
Here, [N] is the spectral intensity of nitrogen, [O] is the spectral intensity of oxygen, and [C] is the spectral intensity of carbon. The precoated metal sheet according to claim 1, wherein the _Nc-max is 0.5 or more.   The pigment contained in the top coating layer or both the top coating layer and the intermediate coating layer is selected from red pigments, yellow pigments, orange pigments, metallic pigments, and pearl pigments. The precoat metal plate of Claim 1 or 2 which is 1 type, or 2 or more types.   The precoat metal plate according to claim 1 or 2, wherein the top coating layer is a clear coating containing no pigment.   The precoat metal plate according to any one of claims 1 to 4, wherein the top coating layer has a -Si-O- bond in a resin skeleton forming the coating. The aminoplast resin content of the coating material forming the top coating layer is 20 to 50 parts by mass with respect to 100 parts by mass of the binder resin solid content,
The paint forming the top coating layer includes an acidic catalyst neutralized with a volatile basic substance,
The pre-coated metal sheet according to any one of claims 1 to 5, wherein the paint forming the intermediate coating film does not contain an acidic catalyst neutralized with a volatile basic substance.   A metal molded body obtained by molding the precoated metal sheet according to any one of claims 1 to 6 by one or more kinds of processes selected from bending, drawing, overhanging, punching or shearing. . At least two layers of wet-on-wet coating or multilayer coating are simultaneously applied to one or both surfaces of the metal plate to satisfy the following conditions (C), (D), (F), (G), and (H). Baking is performed, The manufacturing method of the precoat metal plate characterized by the above-mentioned.
(C) The coating material that forms the outermost top coating layer contains only an aminoplast resin other than butylated melamine as a crosslinking agent.
(D) coating composition forming the intermediate coated film in contact with said top coating layer, see contains only butylated melamine as a crosslinking agent, butylated melamine content of coating composition forming the intermediate coated film, a binder resin solids It is 20-50 mass parts with respect to 100 mass parts .
(F) The aminoplast resin content of the coating material forming the top coating layer is 20 to 50 parts by mass with respect to 100 parts by mass of the binder resin solid content.
(G) The coating material which forms the said top coating film layer contains the acidic catalyst neutralized with the volatile basic substance.
(H) The coating material forming the intermediate coating film does not contain an acidic catalyst neutralized with a volatile basic substance. The manufacturing method of the precoat metal plate of Claim 8 whose content of the said acidic catalyst is 0.1-1 mass part with respect to 100 mass parts of binder resin solid content.

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