JP2011167922A - Coated metal sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a coated metal sheet in which peeling of a clear layer over time is remarkably suppressed while the visibility of a colored coating material layer through the clear layer is secured and which therefore is excellent weatherability. <P>SOLUTION: The coated metal sheet 1 includes a metal sheet 2, the colored coating material layer 3 formed by applying coating onto the metal sheet 2 and the clear layer 4. The clear layer 4 has visible light transmission property and is laminated on the outer surface of the colored coating material layer 3. The colored coating material layer 3 has ≤0.7% ultraviolet light transmittance in 300 nm wave length when the thickness is ≤7 μm. Even when the colored metal sheet 1 is irradiated with ultraviolet light in outdoor exposure for a long period, deterioration in the colored coating material layer 3 near the interface with the clear layer 4 is suppressed since the colored coating material layer 3 has a prescribed ultraviolet light transmissivity. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a coated metal plate used as a decorative exterior material.

  A coated metal plate (pre-coated plate) obtained by painting a metal plate is widely used for decorative exterior materials such as metal siding and metal doors. Examples of such a coated metal plate include steel plates such as cold-rolled steel plates and hot-rolled steel plates, and coated steel plates obtained by coating a plated steel plate on which a plating coating such as an aluminum-zinc alloy plating coating is formed. is there.

  Painted metal plates are used in an environment where they are exposed for a long period of time outdoors, so high weather resistance is required so that the coating film will not crack, peel, or cause significant discoloration or choking. ing.

  Therefore, components such as pigments, resins, and curing agents for coatings on painted metal plates have been studied, and the weather resistance has been improved by surface treatment of pigments, optimization of resin monomer components, introduction of urethane crosslinking with isocyanate, etc. It is illustrated. However, although a coated metal sheet showing good weather resistance can be obtained in a short period, it has been difficult to maintain high weather resistance over a long period of time.

  In addition, by applying a clear paint on the paint film (color paint layer) containing the colorant to form a clear layer, the weather resistance of the paint film is ensured while ensuring visibility from the outside of the color paint layer. Attempts have also been made to improve performance. However, such a clear layer deteriorates in adhesion with the colored paint layer over time, peels off due to long-term use, or mechanically adheres to the painted metal plate when a long time has passed since painting. In the case of processing, cracks and peeling easily occur (so-called deterioration with time), and sufficient weather resistance cannot be obtained.

  The present applicants include, in the clear layer, a polyester resin composed of a cyclic aliphatic polybasic acid and an aliphatic polyhydric alcohol and not containing an aromatic component, and at least one of an ultraviolet absorber and a light stabilizer. It is found that by improving the adhesion between the clear layer and the colored paint layer, the deterioration of the clear layer due to light can be suppressed, and excellent weather resistance can be imparted to the coating film of the coated metal plate. (See Patent Document 1).

JP 2007-55137 A

  However, the performance improvement is demanded for the coated metal plate, and further improvement is required for the weather resistance.

  The present invention has been made in view of the above-mentioned reasons, the purpose of which is to ensure the visibility of the colored paint layer through the clear layer, while the clear peeling of the clear layer over time is significantly suppressed, The object is to provide a coated metal sheet having excellent weather resistance.

  The coated metal plate according to the present invention includes a metal plate, and a colored paint layer and a clear layer formed by coating the metal plate, the clear layer having visible light permeability, and It is laminated on the outer surface of the colored paint layer, and the colored paint layer has an ultraviolet light transmitting ability such that the ultraviolet light transmittance at a wavelength of 300 nm is 0.7% or less when the thickness is 7 μm.

  For this reason, while the colored paint layer is protected by the clear layer, the colored paint layer can be visually recognized from the outside through the clear layer, and a good appearance is imparted to the coated metal plate by the colored paint layer. Even if this coated metal plate is exposed to ultraviolet rays for a long period of time when exposed outdoors, the colored paint layer has a predetermined ultraviolet light transmission ability, so that deterioration of the colored paint layer near the interface with the clear layer is suppressed. . Thereby, peeling of a clear layer with time is remarkably suppressed.

  In the present invention, the clear layer preferably has an ultraviolet transmittance at a wavelength of 300 nm of 15% or less.

  In this case, the amount of ultraviolet rays that pass through the clear layer from the outside and reach the colored paint layer can be reduced. For this reason, deterioration of the surface layer portion of the colored paint layer can be further suppressed, and the clear layer can be further prevented from peeling with time.

  In the present invention, the colored coating layer preferably contains a colorant in a proportion of 2 to 25% by mass.

  In this case, a good appearance can be imparted to the coated metal plate by the colored paint layer, and breakage such as cracking of the colored paint layer during workability of the painted metal plate can be suppressed.

  In this invention, it is preferable that content of the coloring agent in the said clear layer is 10 mass% or less.

  In this case, the light transparency of the clear layer can be sufficiently secured.

  According to the present invention, while ensuring the visibility of the colored paint layer through the clear layer, the deterioration of the colored paint layer in the vicinity of the interface with the clear layer is suppressed, thereby significantly suppressing the peeling of the clear layer over time. The weather resistance of the coating film can be improved.

It is a schematic sectional drawing of the coating metal plate based on an example of embodiment of this invention.

  Hereinafter, the best mode for carrying out the present invention will be described.

  As shown in FIG. 1, the painted metal plate 1 includes a metal plate 2, and a colored paint layer 3 and a clear layer 4 formed by painting the metal plate 2.

  As the metal plate 2, an appropriate steel plate or the like is used. Specific examples thereof include plated steel sheets such as hot-dip aluminum-zinc alloy-plated steel sheets and hot-dip galvanized steel sheets, and stainless steel sheets. By painting on the metal plate 2, the colored paint layer 3 and the clear layer 4 can be sequentially laminated in this order.

  A chemical conversion treatment layer 5 may be formed on the surface of the metal plate 2 prior to coating. Examples of the chemical conversion treatment layer 5 include a chromate (chromate) treatment layer, a phosphate treatment layer, a silica treatment layer, and a composite oxide film.

  In forming the chromate (chromate) treatment layer, for example, a coating type chromate treatment agent (for example, an aqueous solution containing hexavalent chromium and an inorganic acid such as sulfuric acid) is applied on the surface of the metal plate 2. Thereby, a chromate treatment layer made of a hydrated oxide containing trivalent chromium and hexavalent chromium is formed. In forming the phosphate treatment layer, for example, a phosphate treatment solution (for example, an aqueous solution containing a first phosphate and phosphoric acid) is applied on the surface of the metal plate 2. As a result, a phosphate treatment layer made of the third phosphate is formed. Examples of the type of phosphate include zinc phosphate, manganese phosphate, and iron phosphate. In addition, although the thickness of the chemical conversion treatment layer 5 is adjusted suitably, for example, in the case of a phosphate treatment layer, it can be set as the thickness of the range of 1-2 micrometers.

  If necessary, before forming the colored paint layer 3, the influence of the metal plate 2 on the colored paint is reduced to improve the adhesion of the colored paint layer 3, or rust resistance is imparted to the painted metal plate 1. For example, an undercoat paint layer 6 may be provided. As an undercoat (primer) for forming the undercoat paint layer 6, an appropriate paint such as an epoxy paint, a urethane-modified epoxy paint, a polyurethane resin paint is employed in consideration of the composition of the colored paint layer 3. Is done. If necessary, the undercoat paint may contain a rust preventive pigment mainly composed of chromate or manganese. In forming the silica treatment layer, for example, a silicate treatment agent (for example, a solution containing a silane coupling agent and silica) is applied to the surface of the metal plate 2. Thereby, the hardly soluble chemical conversion treatment layer 5 mainly composed of silica is formed.

  In forming the undercoat paint layer 6, for example, the undercoat paint is applied to the metal plate 2 (or the chemical conversion treatment layer 5 formed on the metal plate 2) by spray coating, bar coating, roller curtain coating, curtain flow coating, Apply by an appropriate method such as roll coating. Next, this undercoat paint is cured and dried by heating with a heating device (heater) such as a hot air drying furnace or a dielectric heating device to form an undercoat paint layer 6. The undercoat paint layer 6 may be composed of two or more layers having different compositions. The thickness of the undercoat paint layer 6 is adjusted as appropriate, but the thickness is particularly preferably in the range of 1 to 7 μm.

  The colored paint layer 3 has an ultraviolet light transmitting ability such that the ultraviolet light transmittance at a wavelength of 300 nm is 0.7% or less when the thickness is 7 μm. That is, regardless of the value of the thickness of the colored paint layer 3 in the actual painted metal plate 1, the ultraviolet light transmittance of the colored paint layer 3 is determined by the ultraviolet transmittance when the thickness of the colored paint layer 3 is 7 μm. Identify.

  The ultraviolet ray transmitting ability of the colored paint layer 3 is such that a colored paint used for forming the colored paint layer 3 is applied and formed under the same conditions as in the case of forming the colored paint layer 3, and a single film having a thickness of 7 μm is formed. It can be specified by producing and measuring the ultraviolet transmittance of the single film at a wavelength of 300 nm. The ultraviolet transmittance is ideally preferably 0%, but the practical lower limit is 0.01%.

  Since the colored paint layer 3 has the ultraviolet ray transmitting ability as described above, peeling of the clear layer 4 with time is remarkably suppressed. The relationship between the ultraviolet light transmitting ability of the colored paint layer 3 and the peeling with time of the clear layer 4 has been found by the inventors' research. Conventionally, suppression of peeling of the clear layer 4 over time has been promoted with a focus on preventing deterioration of the clear layer 4. However, as a result of studies by the present inventors, when the ultraviolet ray permeability of the colored paint layer 3 is high, a portion (surface layer portion) near the interface of the colored paint layer 3 with the clear layer 4 deteriorates with time when exposed outdoors. It became clear. When such deterioration of the surface layer portion of the colored paint layer 3 occurs, even if the clear layer 4 is not deteriorated, the clear layer 4 is easily peeled off together with the surface layer portion of the colored paint layer 3. On the other hand, when the colored paint layer 3 has an ultraviolet light transmission ability such that the ultraviolet light transmittance at a wavelength of 300 nm is 0.7% or less when the thickness is 7 μm, the vicinity of the interface with the clear layer 4 when exposed outdoors. The deterioration with time of the colored paint layer 3 is suppressed. Thereby, peeling of the clear layer 4 with time is remarkably suppressed.

  The colored paint layer 3 can be formed by applying and forming a colored paint on the metal plate 2 (or on the chemical conversion treatment layer 5 or the undercoat paint layer 6 formed on the metal plate 2). . Appropriate resin paints such as polyester resin paints, epoxy resin paints, acrylic resin paints, urethane resin paints, and fluorine resin paints containing colorants such as pigments and dyes may be used as the color paints. it can.

  Among the colorants, as the pigment, organic pigments such as phthalocyanine blue and phthalocyanine green, and glitter pigments such as aluminum powder, mica powder, and pearl powder are preferable. These organic pigments can give a vivid color tone to the colored paint layer 3, and the glitter pigment can give the colored paint layer 3 a glitter and a metallic appearance, and the colored paint layer 3 has excellent decorative properties. The appearance can be imparted. These organic pigments and glitter pigments are poor in weather resistance, but the weather resistance of the colored paint layer 3 is maintained because the colored paint layer 3 has the ultraviolet ray transmitting ability as described above. For this reason, while giving the outstanding external appearance to the coating metal plate 1, peeling with time of the clear layer 4 can be suppressed, and the excellent external appearance of the coating metal plate 1 is maintained over a long period of time.

  Common pigments and extender pigments such as titanium oxide, carbon black, iron oxide yellow, iron oxide red (valve), and colored glass powder can be used as the pigment. It is preferable to use in the range which does not impair.

  Examples of the dye include “AIZEN SPILON dye series” manufactured by Hodogaya Chemical Co., Ltd.

  By appropriately adjusting the types of resins and colorants contained in the colored paint for forming the colored paint layer 3 and the contents thereof, the ultraviolet ray transmitting ability of the colored paint layer 3 as described above can be achieved. it can. The content of the colorant in the colored paint layer 3 is preferably 2% by mass or more, and more preferably 10% by mass or more. In order to adjust the ultraviolet light transmitting ability of the colored coating layer 3 with the colorant, aluminum powder is particularly preferably used as the colorant. It is also preferable to adjust the color tone of the colored paint layer 3 while adjusting the ultraviolet light transmittance of the colored paint layer 3 by using aluminum powder and another colorant in combination. As the content of the colorant is increased, the ultraviolet transmittance of the colored paint layer 3 can be reduced and deterioration of the colored paint layer 3 can be suppressed. However, from the viewpoint of maintaining sufficient flexibility of the colored paint layer 3 and maintaining good workability of the coated metal plate 1, the content of the colorant is preferably 25% by mass or less.

  In order to impart the predetermined ultraviolet ray transmitting ability to the colored paint layer 3, the colored paint and the colored paint layer 3 may contain at least one of an ultraviolet absorber and a light stabilizer.

  As the ultraviolet absorber (UVA), a benzotriazole-based ultraviolet absorber, a hydroxyphenyltriazine-based ultraviolet absorber, or the like can be used, and these can be used alone or in combination of two or more. Examples of such ultraviolet absorbers include product numbers “TINUVIN 384-2”, “TINUVIN 400”, “TINUVIN 411L”, “TINUVIN 900”, “TINUVIN 928” and the like provided by Ciba Specialty Chemicals Co., Ltd. Can be mentioned.

  As the light stabilizer (HALS), an appropriate high molecular weight type hindered amine light stabilizer, hindered amine light stabilizer, or the like can be used. These can be used alone or in combination of two or more. . Examples of such a light stabilizer include product numbers “TINUVIN 111 FDL”, “TINUVIN 123”, “TINUVIN 144”, and “TINUVIN 292” provided by Ciba Specialty Chemicals.

  The contents of the ultraviolet absorber and the light stabilizer in the colored paint layer 3 are appropriately adjusted so that the colored paint layer 3 achieves the predetermined ultraviolet transmittance. However, if these contents are excessive, the colored coating layer 3 may be markedly yellow-colored, and the UV absorber and the light stabilizer are likely to crystallize and aggregate in a low temperature environment during storage of the colored coating. Therefore, it may be difficult to reproduce it. Therefore, when only the ultraviolet absorber is contained in the colored coating layer 3, the content is preferably in the range of 1 to 3% by mass with respect to the total amount of the resin components in the colored coating layer 3, and the light stabilizer When it contains only the amount, it is preferable to make the content into the range of 1-3 mass% with respect to the resin component whole quantity. When the ultraviolet absorber and the light stabilizer are used in combination, the content of the ultraviolet absorber is in the range of 0.5 to 3% by mass relative to the total amount of the resin component, and the content of the light stabilizer is 0 relative to the total amount of the resin component. It is preferable that the amount is in the range of 5 to 3% by mass, and the total amount of both is in the range of 1 to 5% by mass with respect to the total amount of the resin components.

  In applying the colored paint to the metal plate 2, for example, an appropriate technique such as spray coating of the colored paint, bar coating, roller curtain coating, curtain flow coating, roll coating or the like is employed. The colored paint applied to the metal plate 2 can be cured and dried by heating with a heating device (heater) such as a hot air drying furnace or a dielectric heating device to form a colored paint.

  Although the thickness of the colored paint layer 3 is appropriately adjusted, it is particularly preferable that the thickness is in the range of 7 to 20 μm in view of improving the appearance of the coated metal plate 1. If the thickness of the colored coating layer 3 is too small, it becomes difficult to improve the design of the coated metal plate 1 by the colored coating layer 3, and if this thickness is too large, a phenomenon of generating small bubbles and blisters during film formation ( There is a risk that the appearance will deteriorate.

  Next, a clear layer 4 having visible light permeability is formed on the colored paint layer 3. The clear layer 4 can be formed by applying and forming a clear paint on the colored paint layer 3. The visible light transparency of the clear layer 4 may be such that the colored paint layer 3 can be visually recognized through the clear layer 4 from the outside. As long as the colored paint layer 3 is visible, the clear layer 4 may be transparent or translucent, and may be colorless or colored. In particular, the clear layer 4 preferably has a visible light transmittance of 10% or more in a wavelength range of 350 to 800 nm. In this case, the colored paint layer 3 can be sufficiently visually recognized from the outside through the clear layer 4. . The visible light transmittance is more preferably 30% or more. This visible light transmittance is an average value of light transmittance in a wavelength range of 350 to 800 nm. Although the visible light transmittance may be 100%, it is impossible in practice, so the practical upper limit of the visible light transmittance is 97%.

  The clear layer 4 preferably has low ultraviolet transmittance, and particularly preferably has an ultraviolet transmittance of 15% or less at a wavelength of 300 nm. In this case, it is possible to reduce the amount of ultraviolet light that passes through the clear layer 4 from the outside and reaches the colored paint layer 3. For this reason, deterioration of the surface layer portion of the colored paint layer 3 can be further suppressed, and peeling of the clear layer 4 with time can be further suppressed. The clear layer 4 preferably has a lower ultraviolet transmittance. In addition, the peeling suppression effect of the clear layer 4 is particularly effectively exhibited when the ultraviolet transmittance of the clear layer 4 is 2% or more. That is, peeling of the clear layer 4 is particularly problematic when the UV transmittance of the clear layer 4 is 2% or more, but even in this case, the UV light transmission when the thickness of the colored coating layer 3 is 7 μm. If the rate is 0.7% or less, peeling of the clear layer 4 is sufficiently suppressed.

  The clear layer 4 has a visible light transmittance and an ultraviolet transmittance that are formed by applying a clear paint used for forming the clear layer 4 under the same conditions as those for forming the clear layer 4. Can be specified by producing a single film having the same thickness as that of the film and measuring the visible light transmittance and ultraviolet transmittance of the single film.

  Examples of the clear paint include appropriate polyester resin-based paints and fluororesin-based paints that can form a layer having visible light permeability. In particular, it is preferable to use a polyester resin-based paint having good weather resistance as the colored paint and the clear paint. In this case, an expensive fluorine-based resin paint is not used, and the adhesion of the clear layer 4 to the colored paint layer 3 is increased.

  When a polyester resin-based paint is used as the clear paint, the clear paint preferably contains a cyclic polyester resin as the polyester resin. In this case, the ultraviolet transmittance of the clear layer 4 can be sufficiently reduced, and the weather resistance of the clear layer 4 is increased, so that cracking, peeling, discoloration, gloss deterioration, etc. due to deterioration of the clear layer 4 are caused. It becomes difficult to occur. Examples of the cyclic polyester resin include a polyester resin having a structure in which a monomer component containing a cyclic aliphatic polybasic acid and an aliphatic polyhydric alcohol and not containing an aromatic component is ester-polymerized. When a chain acid monomer or an aromatic monomer is included as a monomer component, it becomes difficult to sufficiently suppress the ultraviolet transmittance of the clear layer 4 and sufficient adhesion of the clear layer 4 to the colored paint layer 3 is obtained. In addition, the clear layer 4 may be cracked, peeled, discolored, deteriorated in gloss, or the like when exposed to the outdoors for a long time, and sufficient weather resistance may not be obtained. An example of the cycloaliphatic polybasic acid is hexahydrophthalic anhydride. Examples of the aliphatic polyhydric alcohol include 1,6-hexanediol, neopentyl glycol, hydrogenated bisphenol A, and the like.

  In order to adjust the ultraviolet transmittance of the clear layer 4, the clear paint and the clear layer 4 may contain at least one of the same ultraviolet absorber and light stabilizer as described above. In this case, the weather resistance of the clear layer 4 is further improved.

  The contents of the ultraviolet absorber and the light stabilizer in the clear layer 4 are appropriately adjusted so that the clear layer 4 has a desired ultraviolet transmittance. However, if these contents are excessive, the clear layer 4 may be markedly yellowed, and the UV absorbers and light stabilizers are likely to crystallize and aggregate in a low temperature environment such as during storage of the clear paint. There is a risk that it will be difficult to regenerate this. Therefore, when only the ultraviolet absorber is contained in the clear layer 4, the content is preferably in the range of 1 to 3% by mass with respect to the total amount of the resin components in the clear layer 4, and only the light stabilizer. When it contains, it is preferable to make the content into the range of 1-3 mass% with respect to the resin component whole quantity. When the ultraviolet absorber and the light stabilizer are used in combination, the content of the ultraviolet absorber is in the range of 0.5 to 3% by mass relative to the total amount of the resin component, and the content of the light stabilizer is the total amount of the resin component. On the other hand, it is preferable that the range is 0.5 to 3% by mass, and the total amount of both is preferably in the range of 1 to 5% by mass with respect to the total amount of the resin components.

  When the colored clear layer 4 is formed, the clear paint and the clear layer 4 may contain a colorant within a range in which the visible light permeability of the clear layer 4 can be maintained. The colorant is not particularly limited as long as the above conditions are satisfied, and examples thereof include titanium coating mica, iron oxide red, iron oxide yellow, and titanium oxide. The content of the colorant is also adjusted as appropriate within the range in which the visible light transmittance of the clear layer 4 can be maintained. In order to sufficiently secure the light transmittance of the clear layer 4, The content is preferably 10% by mass or less.

  In forming the clear layer 4, for example, a clear paint is applied by an appropriate method such as spray coating, bar coating, roller curtain coating, curtain flow coating, roll coating, or the like. Next, this clear paint is cured and dried by heating with a heating device (heater) such as a hot air drying furnace or a dielectric heating device to form a clear layer 4.

  In forming the clear layer 4, the colored paint layer 3 is formed by applying and forming a colored paint, and then the clear paint can be applied and formed on the colored paint layer 3. In addition, after applying the colored paint, it is placed on top of the colored paint before film formation, and then the clear paint is applied by spraying or curtain coater, etc., and then the colored paint and clear paint are simultaneously formed to form a colored paint layer. 3 and clear layer 4 may be formed (wet-on-wet coating). When such wet-on-wet coating is employed, the adhesion between the colored paint layer 3 and the clear layer 4 is further improved.

  The thickness of the clear layer 4 is appropriately adjusted. If the thickness of the colored paint layer 3 is too small, the weather resistance of the clear layer 4 may be insufficient. If this thickness is too large, There is a risk that the appearance (hole) of the hole is likely to occur and the appearance is deteriorated. In particular, the thickness of the clear layer 4 is preferably in the range of 7 to 20 μm.

  In the coated metal plate 1 such as a coated steel plate configured as described above, the colored paint layer 3 is protected by the clear layer 4, and the colored paint layer 3 can be visually recognized from the outside through the clear layer 4. A good appearance is imparted to the coated metal plate 1 by the paint layer 3. Even if this coated metal plate 1 is exposed to ultraviolet rays for a long period of time when exposed outdoors, the colored paint layer 3 has a predetermined ultraviolet light transmission ability, so that the deterioration of the colored paint layer 3 near the interface with the clear layer 4 Is suppressed. Thereby, peeling with time of the clear layer 4 is remarkably suppressed.

[Examples 1 to 13, Comparative Examples 1 to 3]
As the metal plate 2, a 55% aluminum-zinc hot-dip steel plate having a thickness of 0.35 mm was used.

  A chemical conversion treatment agent shown in Table 1 was applied on the surface of the metal plate 2 to form a chemical conversion treatment layer 5. Table 1 shows the adhesion amount in terms of Cr when using the coating type chromate treatment agent, and the adhesion amount in terms of silica when using the silica treatment agent.

  Next, except for Example 6, an undercoat paint was applied to the rust preventive pigment by bar coating, and heated in an electric furnace at a final plate temperature of 210 ° C. for 60 seconds to form the undercoat paint layer 6. Table 1 shows the composition and thickness of the undercoat paint layer 6. In Table 1, UVA is a benzotriazole-based ultraviolet absorber (product number TINUVIN 400 manufactured by Ciba Specialty Chemicals), and HALS is a hindered amine light stabilizer (product number TINUVIN manufactured by Ciba Specialty Chemicals). 144).

  Next, the colored paint layer 3 was formed by applying the colored paint by bar coating and heating it at an ultimate furnace temperature of 210 ° C. for 60 seconds. The composition, appearance, and thickness of the colored paint layer 3 are shown in Table 1.

  Next, a clear paint was applied by bar coating, and the clear layer 4 was formed by heating at a final reached plate temperature of 230 ° C. for 60 seconds in an electric furnace. The composition, appearance and thickness of the clear layer 4 are shown in Table 1.

[Evaluation test]
(Optical transparency)
Using the clear paint used in each Example and Comparative Example, a single film having the same thickness as that of the clear layer 4 was produced by coating and forming under the same conditions as those for forming the clear paint. Using a spectrophotometer (manufactured by Hitachi, Ltd., model number U-3300), the transmittance of the blank is set to 100% for the visible light transmittance of wavelength 350 to 800 nm and the ultraviolet transmittance of wavelength 300 nm of this single film. As measured.

  A single film having a thickness of 7 μm was prepared by applying and forming a coating film under the same conditions as those for forming the colored coating layer 3 using the colored coatings used in the examples and comparative examples. The ultraviolet transmittance at a wavelength of 300 nm of this single film was measured using a spectrophotometer (manufactured by Hitachi, Ltd., model number U-3300) and the transmittance of the blank as 100%.

(appearance)
The appearance of the painted metal plate was visually observed, and as a result, the colored paint layer 3 was visually recognized and no coating defects were observed, and the colored paint layer 3 was hardly visible or the coating defects were recognized as x. evaluated.

(Accelerated weather resistance test)
For the coated metal plate 1 obtained in each of the examples and comparative examples, a super accelerated weathering tester (manufactured by Iwasaki Electric, model number SUV-F2) and a moisture resistance tester (model number CT-3, manufactured by Suga Test Instruments Co., Ltd.) Used, UV irradiation test under conditions of irradiation time of 24 hours, black panel temperature of 63 ° C. and UV intensity of 100 mW / cm ² , wetting under conditions of test time of 24 hours, tank temperature of 50 ° C. and tank humidity of 98% or more The test cycle which makes a test 1 cycle was repeated 10 cycles.

After sticking the cellophane adhesive tape to the clear layer 4 of the coated metal plate 1 after the test, the presence or absence of peeling of the clear layer 4 when peeled off was confirmed, and the result was evaluated according to the following criteria.
(Double-circle): The peeling of the clear layer 4 is not recognized.
○: The peeling of the clear layer 4 is observed in an area of less than 5% of the clear layer 4.
Δ: Peeling of the clear layer 4 is observed in an area of 5% or more and less than 30% of the clear layer 4.
X: Peeling of the clear layer 4 is recognized in an area of 30% or more of the clear layer 4.

  Further, the gloss and hue of the surface on which the coated metal plate 1 was coated were measured before and after the accelerated weather resistance test, and based on this, the gloss retention and hue change were derived. The results were evaluated according to the following criteria. The gloss and color difference were measured using a color difference meter (color difference meter SM45 manufactured by Suga Test Instruments Co., Ltd.). The gloss retention (%) is a value derived based on the 60 ° specular gloss after the test. The hue change is a color change (ΔE) before and after the test derived by the Hunter color difference formula.

Gloss retention ◎: 70% or more.
○: 50% or more and less than 70%.
Δ: 30% or more and less than 50%.
X: Less than 30%.

Hue change A: 3.0 or less.
A: Greater than 3.0 and 6.0 or less.
(Triangle | delta): It is larger than 6.0 and is 9.0 or less.
X: Greater than 9.0.

(Bending adhesion test)
The coated metal plate 1 obtained in each example and comparative example is bent 180 ° with the surface coated at room temperature of 20 ° C. being the outside and two plates of the same thickness as the coated metal on the inside It was. A cellophane adhesive tape was applied to the surface of the bent portion of the painted metal, and after it was attached by rubbing thoroughly with fingers, it was immediately peeled off. In this case, the presence or absence of peeling of the clear layer 4 was confirmed, and the result was evaluated according to the following criteria.
A: No cracking or peeling is observed in the clear layer 4 B: Cracking is observed in the clear layer 4 but no peeling is observed.
Δ: Peeling of the clear layer 4 is observed in an area of less than 5% of the clear layer 4.
X: Peeling of the clear layer 4 is recognized in an area of 5% or more of the clear layer 4.

(Salt spray test)
The end face of the coated metal plate 1 obtained in each of the examples and the comparative examples is sealed with a rust-proof paint, and two scratches crossing the cross with a cutter knife are applied to the surface of the painted metal plate 1 coated. This was used as a test sample. A salt spray test was performed for 500 hours on this test sample by a test method defined in JIS K5400 9.1. After the test, the surface of the test sample on which the coating was applied was observed, and the occurrence of blisters was confirmed on the part that was not scratched and the part that was scratched. The results were evaluated according to the following evaluation criteria.
(Double-circle): The blister of the part by which there is no abnormality in the part with no damage | wound, and the damage | wound is 3 mm or less on one side.
○: The blister of the part which is not abnormal in the part which is not scratched, and is scratched is 10 mm or less on one side.
(Triangle | delta): A blister generate | occur | produces in the part with no damage | wound, and there is no abnormality in the part with the damage | wound.
X: Blister occurs in both the unscratched part and the scratched part.

1 Painted metal plate 2 Metal plate 3 Colored paint layer 4 Clear layer

Claims (4)

A metal plate, and a colored paint layer and a clear layer formed by coating the metal plate;
The clear layer has visible light permeability and is laminated on the outer surface of the colored paint layer;
A coated metal plate, wherein the colored paint layer has an ultraviolet light transmitting ability such that an ultraviolet light transmittance at a wavelength of 300 nm is 0.7% or less when the thickness thereof is 7 μm.   The painted metal plate according to claim 1, wherein the clear layer has an ultraviolet transmittance of 15% or less at a wavelength of 300 nm.   The said coating material layer contains a coloring agent in the ratio of 2-25 mass%, The coating metal plate of Claim 1 or 2 characterized by the above-mentioned.   Content of the coloring agent of the said clear layer is 10 mass% or less, The painted metal plate as described in any one of Claim 1 thru | or 3 characterized by the above-mentioned.

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