JP2011251253A - Method of forming multilayer coating film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multilayer coating film having a silver metallic coated color with an excellent design.SOLUTION: There is provided a method of forming the multilayer coating film of a silver metallic coated color having a lightness L* (15°) of ≤115, a lightness L* (45°) of ≥60 and a lightness L* (110°) of ≤35 includes: forming a base coating film containing interference mica pigment (A) having a dark region and aluminum pigment (B) having 5-16 μm average particle diameter on a base material; and forming a clear coating film layer. The concentration (PWC) of total content of the interference mica pigment (A) having a dark region and the aluminum pigment (B) is 5-15 mass% and the ratio (A/B) by mass of the interference mica pigment (A) to the aluminum pigment (B) is 2/8-(4/6).

Description

  The present invention relates to a method for forming a multilayer coating film having a unique and excellent design that can be applied to the coating of automobile bodies and the like.

  A plurality of coating films having various roles are sequentially formed on the surface of a base material such as an automobile body to protect the base material and at the same time impart a beautiful appearance and an excellent design. As a method of forming a multilayer coating film, a method of forming an undercoating film such as an electrodeposition coating film on a substrate having excellent conductivity and further forming an intermediate coating film and an overcoating film on the base coating film. Is common. In particular, the top coat film comprising a base coat film and a clear coat film greatly affects the appearance and design of the coat film. In particular, in automobiles, the appearance and design of a top coating film composed of a base coating film and a clear coating film are extremely important. Also, recently, consumers tend to prefer metallic colors over solid colors. The metallic paint color has an effect of emphasizing a design having a complicated shape such as an automobile. In particular, it has an effect of strongly emphasizing a press line of a fender portion and a door portion that can be seen from the outside and are well exposed to light. Such an effect is due to the glittering pigment contained in the coating film, and the reflection angle of light changes in a complex shape part having such irregularities on the automobile, so that the design of the automobile itself can be achieved. The effect of the metallic coating is extremely high. Recently, not only the so-called highlight areas where the light hits well, such as the fender part that characterizes the design of automobiles and the press line of the door part, but also high shades are required in the shaded part of the shade. It has become.

  As a paint color of the metallic paint film applied to the automobile body, a bright silver paint color is the most common. The silver-based paint color can be obtained by blending a bright pigment such as an aluminum pigment (generally metallic aluminum) with the paint. However, when an aluminum pigment such as metallic aluminum is blended, a bright metallic coating with a glittering metallic feeling (so-called particle feeling) can be formed, but when exposed to strong light, the glittering feeling is further emphasized and cheaply glaring. Shine and inferior to luxury. Also, in the highlight area where the light hits the most, the light is strongly reflected and shines more glaringly, so the design of the surrounding car body, especially the press line and its shade part may not be seen well .

  Therefore, when coloring pigments such as carbon black are blended with a silver-based paint film to suppress glare (particle feel), the paint color such as so-called gray metallic or gun metallic can be achieved, and glare (particle feel) can be suppressed. However, the impression (a feeling of being supple, feeling of being supple) that becomes supple (strong) becomes strong, and it becomes difficult to make the design of the car body stand out. Further, when a color pigment such as carbon black is used, the coating color tends to be yellowish. Furthermore, recently, there are coating colors such as so-called titanium gray in which titanium or the like is blended in order to give a high-class feeling to the silver-based coating color. However, when titanium is blended, the yellow color of the coating color becomes stronger and the feeling of smoothness (feeling of being light) becomes stronger. In this way, when carbon black, titanium, etc. are blended in the coating film, it becomes a so-called gray-based metallic coating color with a strong yellowness and a feeling of smoothness (feeling of lightness), and a high-class feeling that suppresses the feeling of glare (particle feeling) There is no bright silver metallic paint color.

  Patent Document 1 (Japanese Patent Application Laid-Open No. 2001-164191) discloses a coating composition that gives a metallic coating depth and brings a high-class feeling. However, the metallic coating film disclosed in Patent Document 1 contains an aluminum flake pigment and two types of interference pigments (interference mica pigment having a dark region and other interference pigments) as essential components. Since a coloring pigment such as carbon black may be included, a gray-based coating film is formed in the same manner as described above. Further, the metallic coating disclosed in Patent Document 1 is characterized in that it exhibits interference color even in the case of a dark color system, and does not cause white blur even in the shade part, and has high brightness. A so-called silver metallic coating film cannot be deepened to give a high-class feeling. Similarly, in Patent Document 2 (Japanese Patent Application Laid-Open No. 2001-164197), two types of interference mica pigments (interference mica pigments having a dark region) and the purpose of giving a coating film depth and providing a high-class feeling, A coating composition containing other mica pigments) as an essential component is disclosed. However, the coating film disclosed in Patent Document 2 is limited to a dark color coating color, and this coating film has an interference color in the dark color system and does not cause white blur in the shade portion. It is characterized by that. Further, since the coating composition disclosed in Patent Document 2 is intended to be a dark paint color, it does not contain a glittering pigment such as an aluminum pigment as an essential component, and is deep in a so-called silver metallic paint film. Can not bring.

  In addition, as disclosed in Patent Document 3 (Japanese Patent Application Laid-Open No. 2007-106925), a metallic coating film having low brightness, high saturation, excellent depth and denseness can be formed, but a metallic film such as a so-called silver metallic coating film having high brightness can be formed. It is very difficult to give a sense of depth to a coating film and bring a sense of quality. Moreover, in a silver metallic coating film having high brightness, it is very difficult to suppress the glare (particle feeling) of the aluminum pigment while giving a sense of depth.

JP 2001-164191 A JP 2001-164197 A JP 2007-106925 A

  An object of this invention is to provide the multilayer coating film which has the silver metallic coating color of the outstanding design which is not in the past. In particular, in the present invention, the glittering sensation (metal particle sensation) based on the aluminum pigment often seen in silver metallic coatings containing a conventional aluminum pigment as a lustrous pigment is suppressed, and the depth, particularly not only the highlight portion, is suppressed. An object of the present invention is to provide a multilayer coating film having a unique design (hereinafter referred to as darkness, finally feeling) having a depth in the shade portion.

  As a result of intensive studies, the present inventor used “interference mica pigment having a dark region” (A) and “aluminum pigment having an average particle diameter of 5 to 16 μm” (B) in combination at a specific ratio and amount. Furthermore, by making the brightness, in particular, the L * (15 °) value 115 or less, the L * (45 °) value 60 or more, and the L * (110 °) value 35 or less, unique The present inventors have found that a multilayer coating film having a good design (dark feeling, finally feeling) can be obtained, and the present invention has been completed. Therefore, this invention provides the formation method of the following multilayer coating films.

On the substrate, a base coating layer containing an interference mica pigment (A) having a dark region and an aluminum pigment (B) having an average particle diameter of 5 to 16 μm is formed, and further a clear coating layer is formed. Formation of a multi-layer coating film having a silver coating color with an L * (15 °) value of 115 or less, an L * (45 °) value of 60 or more, and an L * (110 °) value of 35 or less A method,
The concentration (PWC) of the total content of the interference mica pigment (A) having the dark area and the aluminum pigment (B) is 5 to 15% by mass, and
The mass ratio (A / B) of the interference mica pigment (A) having the dark area and the aluminum pigment (B) is 2/8 to 4/6.
A method for forming a multilayer coating film.

  In the above-described method for forming a multilayer coating film of the present invention, the interference mica pigment (A) having the dark region preferably has an average particle size of 5 to 25 μm.

  The present invention also relates to a multilayer coating film obtained by the above-described method for forming a multilayer coating film of the present invention.

  INDUSTRIAL APPLICABILITY The present invention can provide a silver metallic coating film having an unprecedented unique design (dark feeling, finally feeling). The silver metallic coating film of the present invention has a unique design expressed by terms such as “darkness” and “mostly feeling”. For example, ink used in calligraphy or ink painting is used as water. This means a three-dimensionally deep black particle sensation that can be visually observed when diluted with water and watermarked. Therefore, the silver metallic coating film of the present invention has a unique sense of depth and depth as if the black particles were floating while being a silver-based high-brightness paint color. For this reason, the silver metallic coating film of the present invention has no feeling of fluffy or yellowing like a conventional gray metallic coating film using carbon black or titanium, and has a neat and firm feeling. There is a feeling.

  In addition, the silver metallic coating film of the present invention has a glittering sensation (based on an aluminum pigment) that is often seen in conventional silver coating using an aluminum pigment even when it is strongly exposed to light (that is, a highlight portion). In other words, there is no bright (white) metal particle feeling), and it shines gently and gently. This is considered to be due to the synergistic effect of the specific particle size of the aluminum pigment used in the present invention and the “darkness” (blackness).

  Furthermore, when the silver metallic coating film of the present invention is applied to a base material (coating object) such as an automobile body, it is a highlight that light from bonnets, fenders, doors, etc. having a complicated press line characterizing the design of the automobile itself. The shape of the part can be highlighted. In addition, as described above, the silver metallic coating film of the present invention does not reflect strongly with glare, so the shade portion, particularly the portion where the angle changes suddenly such as a press line and forms a contrast with the highlight portion. You can see the shape of

  Further, the silver metallic coating film of the present invention is a silver-based coating film, that is, although it has a high brightness, it has a “darkness” (black particle feeling). Gives the impression that particles are accumulating, and makes the shade part stand out more black. Furthermore, the silver metallic coating film of the present invention is not yellowish as in the case of using conventional carbon black or titanium even in the shade part, so there is no feeling of smoothness (a feeling of lightness) at all, and the highlight part A strong contrast can be formed.

It is a figure which shows typically the measuring method of lightness (L * value). It is a figure which shows typically a feeling of darkness / at last.

  The multilayer coating film formed by the method of the present invention comprises a base coating layer containing an interference mica pigment (A) having a dark region and an aluminum pigment (B) having an average particle size of 5 to 16 μm on a substrate. It is formed by forming a clear coating layer, and has a silver coating color. The silver coating color of the multilayer coating film formed by the method of the present invention can be defined by brightness according to “JIS Z8729”. In general, the lightness indicates a black color as the value decreases (that is, low lightness), and the whiteness indicates that the value increases (that is, high lightness).

  More specifically, the brightness is defined as “L * value” in the “L * a * b * color system” (CIE 1976), which is an index used to represent the color of the object to be measured. Is. As described above, the lightness (L * value) means that the whiteness of the measured substance increases as the numerical value increases, and the blackness of the measured substance increases as the numerical value decreases.

In the L * a * b * color system (CIE 1976), the a * value and the b * value are referred to as a chromaticness index and are indices indicating chromaticity.
The a * value is based on 0. If the numerical value is negative (-), it means that the greenness of the measured substance increases. If the numerical value is positive (+), the redness of the measured substance is It means to increase.
The b * value is based on 0. When the numerical value is negative (−), it means that the blueness of the measured substance increases. When the numerical value is positive (+), the yellowness of the measured substance is It means to increase.
When both a * value and b * value are 0, it means an achromatic color.

  The lightness (L * value) is measured using a variable angle color difference meter such as “CM512m-3” (Minolta variable angle color difference meter) or X-Rite MA68II (X-Right variable angle color difference meter), for example. be able to.

  Further, in a metallic paint color such as a silver paint color, the lightness (L * value) varies depending on the viewing angle, the incident angle of light, and the reflection angle. Therefore, in the present invention, as shown in FIG. It is defined by “L * (15 °) value”, 45 ° lightness “L * (45 °) value”, and 110 ° lightness “L * (110 °) value”.

  As shown in FIG. 1, the lightness value measured when light is incident on the coating film at an angle of 45 ° and reflected at the same 45 ° angle is defined as “L * (0 °) value”. . Further, the brightness values measured at positions shifted by 15 °, 45 °, and 110 ° from the position where the “L * (0 °) value” is measured to the incident light side are respectively 15 ° brightness “L * (15 °)”. Value ”, 45 degree lightness“ L * (45 °) value ”, and 110 degree lightness“ L * (110 °) value ”.

  The method of the present invention is mainly intended for the painting of automobile bodies, and the lightness “L * (15 °) value” is a portion of the automobile body that is exposed to light, for example, a bonnet, fender, door portion. The lightness “L * (110 °) value” is a portion of the automobile body that is not exposed to light, for example, the lower side of the door ( It defines the brightness at the so-called “shade part” such as the ground side). The lightness “L * (45 °) value” defines lightness in an intermediate region between the “highlight portion” and the “shade portion”.

  The L * (15 °) value representing the lightness of the silver-coated multilayer coating film formed by the method of the present invention is 115 or less, preferably 100 to 114, more preferably 105 to 113. As schematically shown in FIG. 1, the L * (15 °) value defines the brightness at the so-called highlight portion where the light hits well on an object to be coated such as an automobile body. Usually, in a conventional silver-based paint color using an aluminum pigment, the lightness (L * (15 °) value) greatly exceeds 115 and becomes a value of 120 to 180 in such a highlight portion. In general, for example, in the case of a plating-like silver coating color, it may greatly exceed 300. As described above, in the silver-based paint color using the conventional aluminum pigment, in the highlight portion, the glitter of the aluminum pigment used itself becomes strong, and the L * (15 °) value greatly exceeds 115, which is cheap. Irritably vulgarly glittering and whitish, lacking luxury. When the L * (15 °) value is 115 or less as in the present invention, the multi-layer coating film exhibits a silver coating color, but has a glittering feeling (metal particle feeling) based on the conventional aluminum pigment itself. ), And a sense of luxury. This is also one of the synergistic effects brought about by using the aluminum pigment (B) having an average particle size of 5 to 16 μm. Further, in the present invention, by using a combination of the aluminum pigment (B) and the interference mica pigment (A) having a dark part region, the silver coating color is called “darkness” or “just feeling”. Design can be given.

  “Darkness” or “Feeling” is a word that expresses a unique design given to the silver paint color according to the present invention. To explain in an easy-to-understand manner, as shown schematically in FIG. Is it a particle feeling that can be visually observed when the ink used in ink painting etc. is diluted with water and watermarked with light, as if black particles are scattered in three dimensions? This means a black particle feeling with a strange floating feeling. Therefore, in the present invention, a silver paint color having a high lightness, in particular, an L * (15 °) value of 115 or less is shown. Further, when the coating film is observed closely, black particles are scattered three-dimensionally. Thus, it is possible to provide a coating film with a unique design that has a unique floating feeling, transparency, depth feeling, and depth feeling that has never existed. Such “dark feeling” or “just feeling” may not be visible when the L * (15 °) value exceeds 115. In addition, in the highlight part where the light of the car body hits strongly, it is possible to suppress the glittering feeling (metallic particle feeling) based on the aluminum pigment by such a “dark feeling” or “motivated feeling”. A gentle, unprecedented high-class silver color (at last). Further, in an automobile body or the like, it is possible to highlight the formation of a highlight portion, such as a bonnet, a fender, or a door, having a complicated press line that characterizes the design of the automobile. In addition, as described above, since it does not reflect strongly in the highlight portion, the shape of the shade portion, particularly the portion that forms a contrast with the highlight portion by changing the angle suddenly in the press line or the like is good. Become visible.

  In particular, it should be noted that in the present invention, such “darkness” or “just feeling” is more emphasized when reflected at a shallow angle with respect to incident light. For example, as schematically shown in FIG. 1, at a position shifted by 110 ° to the incident light side from a position (0 °) where the incident light is regularly reflected on the coating film, a position generally called a shade portion of an automobile body, This “darkness” or “just feeling” is the strongest, especially in the lower part of the fender and door (the part close to the floor) and the side skirt, even though it is colored in silver, it is even more emphasized. At first glance, it is possible to give a black particle feeling as if black particles are accumulated, and to make the car body more prominent (to give a tight impression). Furthermore, in the multi-layer coating film of the present invention, the shade part does not have a yellowish color as in the case of using conventional carbon black or titanium, so there is no feeling of smoothness (feeling soft), the highlight part and Strong contrast can be formed.

  In addition, the “darkness” or “moist feeling” according to the present invention is abrupt between the highlight portion and the shade portion, unlike the flip-flop (FF) effect using an aluminum pigment, particularly a large aluminum pigment. The brightness does not change.

  Therefore, as schematically shown in FIG. 1, the L * (110 °) value representing the lightness in the shade portion is 35 or less, preferably 25 to 34, more preferably 30 to 33. The L * (45 °) value representing the brightness of the intermediate part with the part is 60 or more, preferably 61 to 70, more preferably 62 to 65. In the present invention, since the lightness (L * (45 °) value) of the intermediate portion is 60 or more, the lightness does not change abruptly between the highlight portion and the shade portion. In addition, not only in press lines, but also in continuously curved portions and dynamically undulating portions, the impression and brightness changes that are completely different from the flip-flop (FF) effect are observed in objects such as automobile bodies. Can be given.

  When the L * (110 °) value exceeds 35, the brightness of the aluminum pigment is noticeable, the shade part becomes bright (white), and the “darkness” or “feeling at last”, that is, the feeling of black particles becomes inconspicuous.

  On the other hand, when the L * (45 °) value is less than 60, a moderate brightness change from the highlight portion to the shade portion does not appear, and the flip-flop (FF) effect due to the aluminum pigment appears strongly, ie, high Since the intermediate portion between the light portion and the shade portion becomes dark, the unique “darkness” or “feeling at last” (black particle feeling) in the shade portion is not noticeable.

  Thus, the multi-layer coating film of silver coating color formed according to the present invention has a unique “darkness” or “motivated feeling” from the highlight portion to the shade portion, particularly in the shade portion, There is no impression (smoothness) or yellowness like a conventional gray metallic coating film using black or titanium, and it gives a clean and firm impression, creating an unprecedented luxury.

  Hereinafter, the formation method of the multilayer coating film of this invention and the coating composition which forms each coating film layer are demonstrated in detail.

  The present invention provides a top coating film by applying a base coating composition on a substrate to form a base coating layer, and further applying a clear coating composition thereon to form a clear coating layer. As described above, a multilayer coating film including a base coating film layer and a clear coating film layer can be formed. As described above, the multilayer coating film obtained by the method of the present invention has a silver coating color, has a lightness L * (15 °) value of 115 or less, and an L * (45 °) value of 60 or more. In addition, the L * (110 °) value is 35 or less, and the hue continuously changes from the highlight portion to the shade portion of the article having complicated irregularities such as an automobile body, Providing a unique design that is not known as “darkness” or “finally”.

Base Coating Composition In the present invention, the base coating composition capable of forming a base coating layer is an interference mica pigment (A) having a vehicle and a dark area [hereinafter referred to as “interference mica pigment ( A) ”or“ pigment (A) ”in some cases, and an aluminum pigment (B) having an average particle diameter of 5 to 16 μm [hereinafter referred to as“ aluminum pigment (B) ”or“ pigment ”. (B) may be abbreviated as “]” in a specific amount.

  In the present invention, a glitter coating layer is formed from a glitter coating composition containing pigment (A) and pigment (B) in specific amounts, respectively, and a clear coating layer is further formed thereon. Thus, it is possible to form a multilayer coating film having a silver coating color having a unique design called “darkness” or “just feeling” and having continuously changing brightness.

Pigment (A)
The pigment (A) (interference mica pigment having a dark region) exhibits a black or almost black interference color. Specifically, the surface of the flaky mica particles is coated or deposited with various substances in the dark region. Things apply. For example, an interference mica pigment coated with a titanium compound containing low-order titanium oxide and then coated with titanium dioxide is preferable. The interference mica pigment (A) is preferably a scaly pigment having an average particle diameter of 5 to 25 μm, preferably 5 to 15 μm, more preferably 5 to 10 μm. If the average particle size of the pigment (A) is less than 5 μm, it becomes a gray metallic or gun metallic coating color, which can suppress glare (particle feeling), but has a strong impression (feeling smooth). There is a risk of problems such as making it difficult to make the design of the car body stand out. If it exceeds 25 μm, it will be difficult to suppress the glare (particle feeling) while giving a deep feeling to the bright silver coating, Moreover, there is a risk of problems such as deterioration in appearance. The average particle size of the pigment (A) used in the present invention is to measure particle size distribution by a laser diffraction method, showing a median value (D _50).

  Examples of the interference mica pigment (A) include “Infinite Color Black Diamond” (reduced mica) (manufactured by Shiseido), “Infinite Color BP-15” (manufactured by Shiseido), “Black Olive OCO3Z” (manufactured by BASF), and the like. Can be used. Among these, as the interference mica pigment (A), “Infinite Color Black Diamond” (manufactured by Shiseido Co., Ltd.) is particularly preferable because of its narrow particle size distribution.

  The concentration (Pigment Weight Concentration (PWC)) of the interference mica pigment (A) in the base coating composition is 1 to 5% by mass, preferably 2 to 4% by mass. If the PWC of the interference mica pigment (A) is less than 1% by mass, there may be a problem that it is difficult to suppress glare (particle feeling) while giving a deep feeling to the silver coating with high brightness. If it exceeds 5% by mass, it becomes a coating of gray metallic or gun metallic, which can suppress the glare feeling (particle feeling), but the impression of a feeling of softness (feeling soft) becomes too strong and stands out from the design of the car body. There is a risk of problems such as difficulty.

  In this invention, the density | concentration (PWC) of a pigment (A) represents the mass of a pigment (A) with a percentage (mass%) with respect to the mass of the total solid of a base coating composition. The total solid content of the base coating composition includes all of the pigment (A) and pigment (B), the resin component (solid content) that serves as the vehicle of the base coating composition, and any other components (solid content). It is.

Pigment (B)
The pigment (B) (aluminum pigment) is a pigment that imparts concealability and metallic feeling, and is an aluminum pigment having an average particle diameter of 5 to 16 μm, preferably 10 to 16 μm, more preferably 13 to 16 μm. There is no limitation in particular and what is used in the said field | area of a metallic paint can be applied suitably. When the average particle size of the pigment (B) is less than 5 μm, it becomes a coating film of gray metallic and gun metallic, which can suppress glare feeling (particle feeling), but the impression that it is soft (feeling light) becomes stronger. Therefore, there is a fear that it becomes difficult to make the design of the vehicle body stand out, and when it exceeds 16 μm, there is a possibility that the concealability is lowered and the appearance is deteriorated. The average particle size of the pigment (B) used in the present invention is to measure particle size distribution by a laser diffraction method, showing a median value (D _50).

  As the pigment (B), for example, leafing, semi-leafing or non-leafing type aluminum flakes prepared by a usual method of grinding aluminum flakes with a fatty acid such as stearic acid by a ball mill can be mentioned. Leafing aluminum flakes are preferably used. Moreover, the design with the target silver metallic feeling can be obtained also by using a colored aluminum flake pigment.

  The concentration (Pigment Weight Concentration (PWC)) of the aluminum pigment (B) in the base coating composition is 1 to 10% by mass, preferably 3 to 9% by mass, and more preferably 6 to 8% by mass. If the PWC of the aluminum pigment (B) is less than 1% by mass, there is a risk of problems such as a decrease in concealment, and if it exceeds 10% by mass, there is a risk of problems such as poor appearance.

  In this invention, the density | concentration (PWC) of a pigment (B) represents the mass of a pigment (B) with a percentage (mass%) with respect to the mass of the total solid of a base coating composition. The total solid content of the base coating composition includes all of the pigment (A) and pigment (B), the resin component (solid content) that serves as the vehicle of the base coating composition, and any other components (solid content). It is.

  Further, the concentration (PWC) of the total content of the interference mica pigment (A) and the aluminum pigment (B) is 5 to 15% by mass, preferably 8 to 15% by mass, and more preferably 10 to 15% by mass. If the concentration of the total content (PWC) is less than 5% by mass, there is a risk of problems such as a decrease in concealment, and if it exceeds 15% by mass, there is a risk of problems such as poor appearance.

  Furthermore, the mass ratio (A / B) of the interference mica pigment (A) and the aluminum pigment (B) is 2/8 to 4/6, preferably 3/7 to 4/6, which is lower than 2/8. It is possible to suppress the glare feeling (particle feeling) with the paint colors of gray metallic and gun metallic, but the impression that the feeling of softness (feeling of lightness) becomes stronger and it is difficult to make the body design stand out. When the ratio exceeds 4/6, there is a risk that it becomes difficult to suppress a glare feeling (particle feeling) while giving a deep feeling to the silver coating film having high brightness.

  In the present invention, not only the pigment (A) and the pigment (B), but if necessary, other bright pigments other than the pigment (A) and the pigment (B), organic coloring pigments, inorganic pigments You may mix | blend pigments, such as a coloring pigment and extender, with a base coating composition suitably.

The bright pigment other than the pigment (A) is not particularly limited. For example, natural or synthetic alumina (Al ₂ O ₃ ) flakes or mica (mica) flakes and metals other than titanium (for example, iron, Chromium, cobalt, tin, zirconium, etc.) coated with natural or synthetic silica (SiO ₂ ) flakes, for example, titanium, iron, chromium, cobalt, tin, zirconium, etc. , Metal aluminum flakes, metal titanium flakes, stainless steel flakes, glass flakes and the like, and two or more kinds may be used in combination.

  The organic coloring pigment is not particularly limited, and examples thereof include azo pigments (for example, azo chelate pigments, insoluble azo pigments, condensed azo pigments), phthalocyanine pigments, quinacridone pigments, benzimidazolone pigments, Diketopyrrolopyrrole pigment, isoindolinone pigment, selenium pigment, perinone pigment, perylene pigment, indigo pigment, dioxane pigment, quinophthalone pigment, dioxazine pigment, metal complex organic pigment, etc. Two or more kinds may be used in combination.

  The inorganic coloring pigment is not particularly limited. For example, carbon black, titanium oxide, yellow lead, zinc white, cadmium red, molybdenum red, chromium yellow, chromium oxide, Prussian blue, cobalt blue, yellow iron oxide, bengara, etc. And may be used in combination of two or more.

  The extender pigment is not particularly limited, and examples thereof include calcium carbonate, barium sulfate, clay, and talc. Two or more types may be used in combination.

  In the base coating composition, the total pigment concentration (PWC) is 0.3 to 50% by mass, preferably 0.3 to 30% by mass. If the amount exceeds 50% by mass, the finished appearance may be deteriorated.

Vehicle The vehicle contained in the base coating composition that can be used in the present invention is a dispersion of the above-described pigment, and is a film-forming resin and, if necessary, a crosslinking agent (and / or a curing agent). ).

  Examples of the film-forming resin constituting the vehicle include (A) acrylic resin, (B) polyester resin, (C) alkyd resin, (D) epoxy resin, (E) polyurethane resin, and (F) polyether resin. In particular, acrylic resins and polyester resins are preferably used. These can be used in combination of two or more. In addition, the film-forming resin includes a curable type and a lacquer type, but a curable type is usually used. In the case of a curable type, it is used by mixing with a crosslinking agent such as an amino resin, a (block) polyisocyanate compound, an amine, a polyamide, or a polyvalent carboxylic acid, and the curing reaction is carried out at room temperature or at room temperature. Can be advanced. It is also possible to use a film-forming resin of a type having no curability in combination with a type having curability.

(A) Acrylic resin Examples of the acrylic resin include a copolymer of an acrylic monomer, or a copolymer of an acrylic monomer and another ethylenically unsaturated monomer. Acrylic monomers that can be used for the copolymerization include methyl, ethyl, propyl, n-butyl, i-butyl, t-butyl, 2-ethylhexyl, lauryl, phenyl of acrylic acid, methacrylic acid, acrylic acid or methacrylic acid. , Benzyl, 2-hydroxyethyl, 2-hydroxypropyl and the like, ring-opening adducts of caprolactone of acrylic acid or 2-hydroxyethyl methacrylate, acrylamide, methacrylamide and N-methylolacrylamide. Other ethylenically unsaturated monomers copolymerizable with these include styrene, α-methylstyrene (or dimer), itaconic acid, maleic acid, vinyl acetate and the like. Moreover, it is preferable to make an acrylic resin into an aqueous emulsion by a method known to those skilled in the art, for example, a method disclosed in JP-A-2007-39615.

(B) Polyester resin Examples of the polyester resin include saturated polyester resins and unsaturated polyester resins, and examples include condensates obtained by heat condensation of polybasic acids and polyhydric alcohols. Examples of the polybasic acid include saturated polybasic acids and unsaturated polybasic acids. Examples of the saturated polybasic acid include phthalic anhydride, terephthalic acid, succinic acid, and the like. Examples of the acid include maleic acid, maleic anhydride, fumaric acid and the like. Examples of the polyhydric alcohol include dihydric alcohol and trihydric alcohol. Examples of the dihydric alcohol include ethylene glycol and diethylene glycol. Examples of the trihydric alcohol include glycerin and trimethylolpropane. Etc.

(C) Alkyd resins Alkyd resins include the above polybasic acids and polyhydric alcohols, modified oils and fats and fatty acids (soybean oil, linseed oil, coconut oil, stearic acid, etc.), natural resins (rosin, succinic acid, etc.), etc. An alkyd resin obtained by reacting an agent can be used.

(D) Epoxy resin Examples of the epoxy resin include a resin obtained by the reaction of bisphenol and epichlorohydrin. Examples of bisphenol include bisphenol A and F. Examples of the bisphenol type epoxy resin include Epicoat 828, Epicoat 1001, Epicoat 1004, Epicoat 1007, Epicoat 1009 (all manufactured by Shell Chemical Co., Ltd.) and the like, and these can be chained using an appropriate chain extender. Extended ones can also be used.

(E) Polyurethane resin Examples of the polyurethane resin include resins having a urethane bond obtained from various polyol components such as acrylic, polyester, polyether, and polycarbonate and a polyisocyanate compound. Examples of the polyisocyanate compound include 2,4-tolylene diisocyanate (2,4-TDI), 2,6-tolylene diisocyanate (2,6-TDI), and mixtures thereof (TDI), diphenylmethane-4,4 ′. Diisocyanate (4,4′-MDI), diphenylmethane-2,4′-diisocyanate (2,4′-MDI), and mixtures thereof (MDI), naphthalene-1,5-diisocyanate (NDI), 3,3 ′ -Dimethyl-4,4'-biphenylene diisocyanate (TODI), xylylene diisocyanate (XDI), dicyclohexylmethane diisocyanate (hydrogenated HDI), isophorone diisocyanate (IPDI), hexamethylene diisocyanate (HDI), hydrogenated xylylene diene Isocyanate (HXDI) etc. It can be mentioned.

(F) Polyether resin The polyether resin is a polymer or copolymer having an ether bond, and is a polyoxyethylene polyether, polyoxypropylene polyether, polyoxybutylene polyether, bisphenol A, or bisphenol. A polyether resin having at least two hydroxyl groups per molecule such as a polyether derived from an aromatic polyhydroxy compound such as F, or the polyether resin and succinic acid, adipic acid, sebacic acid, phthalic acid, Mention may be made of carboxyl group-containing polyether resins obtained by reacting polycarboxylic acids such as isophthalic acid, terephthalic acid and trimellitic acid, or reactive derivatives such as acid anhydrides thereof.

  When the vehicle contains a cross-linking agent, the ratio of the film-forming resin and the cross-linking agent is preferably 90 to 50% by mass of the film-forming resin and 10 to 50% by mass of the cross-linking agent in terms of solid content. The film-forming resin is 85 to 60% by mass, and the crosslinking agent is 15 to 40% by mass. When the crosslinking agent is less than 10% by mass (when the coating film-forming resin exceeds 90% by mass), the crosslinking in the coating film may not be sufficient. On the other hand, when the cross-linking agent exceeds 50% by mass (when the coating film-forming resin is less than 50% by mass), the storage stability of the coating composition is lowered and the curing rate is increased, so that the coating film appearance is deteriorated. There is.

Other components In addition to the above-mentioned components, the base coating composition that can be used in the present invention includes a polyamide wax that is a lubricating dispersion of an aliphatic amide and a polyethylene wax that is a colloidal dispersion mainly composed of oxidized polyethylene. Such as anti-settling agent, curing catalyst, UV absorber, antioxidant, leveling agent, surface conditioner such as silicon and organic polymer, anti-sagging agent, thickener, antifoaming agent, lubricant, crosslinkable polymer particles (Microgel) etc. can be added suitably. These additives can improve the performance of paints and coating films by blending them at a ratio of 15 parts by mass or less with respect to 100 parts by mass of the vehicle (based on solid content).

  The base coating composition of the present invention is provided in a form in which the above-mentioned constituents are usually dissolved or dispersed in a solvent. Any solvent can be used as long as it dissolves or disperses the vehicle, and an organic solvent and / or water can be used. Examples of the organic solvent include those usually used in the paint field. Examples thereof include hydrocarbons such as toluene and xylene, ketones such as acetone and methyl ethyl ketone, esters such as ethyl acetate, cellosolve acetate and butyl cellosolve, alcohols and the like. From the viewpoint of the environment, it is preferable to use water when the use of the organic solvent is regulated. In this case, an appropriate amount of a hydrophilic organic solvent may be blended.

  In a particularly preferred embodiment, the base coating composition that can be used in the present invention includes the above-described pigment (A) and pigment (B), and a film-forming resin containing an acrylic resin emulsion as a vehicle, an acrylic resin, and It may contain a curing agent containing an aqueous dispersion of a hydrophobic melamine resin having a particle size of 20 to 140 nm obtained by dispersing the reaction product obtained by reacting the hydrophobic melamine resin with water, and a crosslinking agent. Thus, a coating film having excellent color developability can be obtained. In addition, in the method for forming a multilayer coating film in automobile coating, when the above base coating composition is used as a water-based coating, a coating film having excellent recoat adhesion, chipping property, and water-resistant adhesion can be obtained. Accordingly, the above base coating composition can be suitably used as an aqueous base coating composition.

Method for Forming a Coating Film The method for forming a multilayer coating film of the present invention comprises applying the above base coating composition on a substrate to form a base coating layer, and further applying a clear coating composition thereon. Thus, a clear coating film layer is formed, and a multilayer coating film including a base coating film layer and a clear coating film layer is formed on the substrate. In the present invention, the above base coating composition can be suitably used as an aqueous glittering coating for automobiles (automobile bodies, parts, etc.).

  The substrate is not particularly limited, and metals such as iron, aluminum, magnesium, copper, tin, zinc or alloys thereof and molded articles thereof; inorganic materials such as glass, cement and concrete; polyethylene resins, Polypropylene resin, ethylene-vinyl acetate copolymer resin, polyamide resin, acrylic resin, vinylidene chloride resin, polycarbonate resin, polyurethane resin, epoxy resin, polyester resin, polystyrene resin, ABS resin, and various plastics such as FRP Examples include materials and molded articles or foams thereof; natural or synthetic materials such as wood and fiber materials (paper, cloth, etc.). In order to effectively express the unique design obtained by the present invention, the base material has a curved surface such as a car body and parts (car body, door, etc.) such as a passenger car, a truck, a motorcycle, and a bus. It is preferable that Specific examples of the plastic molded product include automobile parts such as a spoiler, a bumper, a mirror cover, a grill, and a door knob. Further, these plastic molded articles are preferably those washed with steam or neutral detergent with trichloroethane. Furthermore, primer coating for enabling electrostatic coating may be applied.

  In the method for forming a multilayer coating film of the present invention, when the base material is an automobile body or its parts, the conductive base material is previously subjected to degreasing treatment or chemical conversion treatment (formation with phosphate, chromate, etc.). After the treatment, it is preferable to apply base coating such as electrodeposition coating or intermediate coating to the base material.

  Electrodeposition coating is performed for the purpose of imparting rust prevention by forming an electrodeposition coating film on a conductive substrate such as a steel sheet. The electrodeposition coating composition that can be used is not particularly limited, and any of a cationic electrodeposition coating composition and an anionic electrodeposition coating composition that are well known to those skilled in the art can be used. From the viewpoint, a cationic electrodeposition coating composition is preferable, and an epoxy cationic electrodeposition coating composition is particularly preferable.

  In the present invention, when the base material is an automobile body or a steel plate, pretreatment up to degreasing, water washing, chemical film formation, water washing, pure water washing, and drying can be performed by a conventionally known method before electrodeposition coating film formation. preferable. As an electrodeposition coating film forming method, an appropriate method may be arbitrarily selected from conventionally known methods. The electrodeposition coating film forming conditions, the bake curing conditions, the thickness of the electrodeposition coating film, etc. What is necessary is just to determine suitably according to the kind of material, the electrodeposition coating composition to be used, etc.

  In the intermediate coating, an intermediate coating layer is formed on the substrate or electrodeposition coating to improve the performance such as concealment of the base, chipping resistance, and adhesion to the top coating layer. Is called. In addition, the intermediate coating layer serves as a base for smoothing the final multilayer coating film to form a coating film with good appearance, and between the electrodeposition coating layer and the top coating layer. And weather resistance against deterioration of the coating film due to ultraviolet rays and water reaching the coating film surface. There are no particular limitations on the intermediate coating composition that can form the intermediate coating layer, and other than solvent-based coatings well known to those skilled in the art, water-based coatings, powder coatings, high solid coatings, etc. Specifically, epoxy ester / melamine resin, alkyd / melamine resin or oil-free polyester / melamine resin paint, acrylic resin and / or polyester resin and amino resin and / or isocyanate curing agent are combined. In addition, it can be appropriately selected from conventionally known intermediate coating materials such as intermediate coating materials.

  Regarding the method of forming the intermediate coating layer, an appropriate method may be arbitrarily selected from conventionally known methods. Further, in the present invention, a gray-based intermediate coating composition comprising carbon black and titanium dioxide as main pigments, a combination of set gray and various colored pigments that match the lightness and hue of the top coat layer, so-called A color intermediate coating composition can be used. These color intermediate coating compositions can develop a composite color of the intermediate coating layer and the top coating layer, and can further enhance the design. Further, flat pigments such as aluminum powder and mica powder may be added to these intermediate coating compositions. Further, the intermediate coating composition may contain additives that can be usually added to the coating, for example, a surface conditioner, an antioxidant, an antifoaming agent, and the like. The dry film thickness of the intermediate coating layer is preferably 20 to 100 μm, more preferably 30 to 50 μm.

  In the method for forming a multilayer coating film of the present invention, preferably, a base coating composition is applied onto a substrate to form a base coating layer, and a clear coating composition is applied onto the base coating layer. To form a clear coating layer.

  If the base material is a base material having a base coating layer that has been subjected to base coating such as electrodeposition coating or intermediate coating, if necessary, wet on wet (W / W) method or wet on dry (W / D) method, a base coating composition can be applied to form a base coating layer. Next, a clear coating composition is applied onto the base coating layer by a wet-on-wet (W / W) method or a wet-on-dry (W / D) method to form a clear coating layer. it can. The W / W method means that after coating the coating composition, the coated film is dried by air drying or the like, or semi-cured at a temperature of less than 100 ° C., if necessary, and uncured or semi-cured. On the other hand, the W / D method is a method in which a coating composition is applied, and then the coating composition is applied and then baked and cured. It is a method of applying a composition.

  The method for applying the base coating composition is not particularly limited. For example, a spray method, a roll coater method, and the like are preferable. From the viewpoint of improving the appearance, multistage coating by air electrostatic spray coating, preferably two stages. A coating method is preferable, in which coating is performed or air electrostatic spray coating is combined with a rotary atomizing electrostatic coating machine called a metallic bell. It is also possible to paint multiple times.

  Although the film thickness of the coating film at the time of application | coating by a base coating composition changes with desired uses, generally 5-30 micrometers is preferable per coat with a dry film thickness, and it is preferable that it is 5-20 micrometers. If the dry film thickness is less than 5 μm, the underlying layer cannot be concealed, resulting in film breakage, and if it exceeds 30 μm, the sharpness may be deteriorated or defects such as unevenness or sagging may occur during painting. There is a fear. In order to obtain a multilayer coating film having a good appearance, it is preferable to heat the formed glittering base coating film at 40 to 100 ° C. for 2 to 10 minutes before applying the clear coating composition. This preheating is preferable because the orientation of the glitter pigment is not disturbed even if the clear coating composition is applied thereon.

  In the present invention, at least one clear coating layer can be formed on the base coating layer thus formed. The clear coating layer smoothes and protects irregularities, flickering, and the like caused by the bright pigment contained in the base coating layer, and further imparts an aesthetic appearance.

  The clear coating composition that can be used in the method for forming a multilayer coating film of the present invention is not particularly limited, and those generally used for top coating can be used. For example, acrylic resin, polyester Use a mixture of at least one thermosetting resin selected from resins, fluororesins, epoxy resins, polyurethane resins, polyether resins and modified resins thereof, and the above-mentioned crosslinking agent and / or curing agent. Can do.

  If necessary, the clear coating composition is a colored pigment, extender pigment, modifier, ultraviolet absorber, leveling agent as long as it does not impair the transparency or does not interfere with the design of the base. It is possible to add additives such as a dispersant and an antifoaming agent. In addition, when the clear paint containing the carboxyl group-containing polymer and the epoxy group-containing polymer described in JP-B-8-19315 is formed with the above-mentioned base coating layer by the acid rain countermeasure and the W / W method, From the viewpoint of not disturbing the orientation of the glitter pigment and the color pigment, it is preferably used. In addition, the clear coating composition can take various forms such as a solvent type, an aqueous type, and a powder type. As the solvent-based paint or water-based paint, a one-component paint may be used, or a two-component paint such as a two-component urethane resin paint may be used.

  Preferred examples of the solvent-based clear coating composition include a combination of an acrylic resin and / or a polyester resin, an amino resin and / or an isocyanate, or a carboxylic acid / epoxy curing system in terms of transparency or acid etching resistance. And acrylic resin and / or polyester resin.

  Examples of the water-based clear coating composition include a resin obtained by neutralizing a film-forming resin contained in the solvent-based clear coating composition described above as an example of the solvent-type clear coating composition with a base to make it water-based. Things can be mentioned. This neutralization can be carried out by adding tertiary amines such as dimethylethanolamine and triethylamine before or after polymerization.

  Furthermore, it is preferable that a viscosity control agent is added to the clear coating composition in order to ensure coating workability. As the viscosity control agent, those generally showing thixotropy can be used. As such a thing, a conventionally well-known thing can be used, for example. Moreover, a curing catalyst, a surface conditioner, etc. can be included if necessary.

  In addition, as a clear coating composition used in the above-mentioned multilayer coating film forming method, Ford Cup No. 20 at 20 ° C. is used from the viewpoint of influence on the environment due to the content of the organic solvent. 4 is a solvent-type clear coating composition or a water-based clear coating composition, or a powder-type clear, in which the solid content of the clear coating composition when diluted to a viscosity of 20 to 50 seconds is 50% by mass or more A coating composition is preferred.

  In the present invention, the clear coating composition may be applied on the cured base coating layer, but the clear coating composition is applied on the uncured or semi-cured base coating layer by the W / W method. It is preferable to apply the composition. The method for applying the clear coating composition described above to the base coating layer is not particularly limited. For example, a spray method, a roll coater method, and the like are preferable. A coating method using a rotary atomizing electrostatic coating machine called a microbell can be mentioned. It is also possible to paint multiple times. When the clear coating composition is applied a plurality of times, it may be baked and cured simultaneously after the final clear coating composition is applied, and it is not necessary to completely cure the previously formed clear coating film.

  On the other hand, as the powder-type clear coating composition, ordinary powder coatings such as thermoplastic and thermosetting powder coatings can be used. A thermosetting powder coating composition is preferred because a coating film having good physical properties can be obtained. Specific examples of the thermosetting powder coating composition include epoxy-based, acrylic-based, and polyester-based powder clear coating compositions, etc., and acrylic-based powder clear coating compositions having good weather resistance. Is particularly preferred.

  As described above, the clear coating layer formed on the base coating layer (which may be uncured, semi-cured, or completely cured) can be used as an electrodeposition coating, an intermediate coating, etc. It can be baked and cured at a predetermined temperature and for a predetermined time together with a base coating layer (which may be uncured, semi-cured or fully cured) to form a multilayer coating.

  The dry film thickness of the clear coating layer formed by applying the clear coating composition is generally preferably 10 to 80 μm, and more preferably 20 to 60 μm. When the dry film thickness is less than 10 μm, the unevenness of the foundation cannot be concealed, and when it exceeds 80 μm, there is a possibility that problems such as peeling or sagging may occur during coating.

  The clear coating film thus formed forms a cured coating film by simultaneously heating together with a preliminarily formed glitter base coating film. The heat curing temperature is preferably set to 80 to 180 ° C., more preferably 120 to 160 ° C., from the viewpoints of curability and physical properties of the obtained multilayer coating film. Although the heat curing time can be arbitrarily set according to the above temperature, it is appropriate that the heat curing temperature is 120 ° C. to 160 ° C. and the time is 10 to 30 minutes.

  Thus, the film thickness of the multilayer coating film formed is generally 30 to 300 μm, and preferably 50 to 250 μm. When the film thickness is less than 30 μm, the strength of the film itself decreases, and when it exceeds 300 μm, film physical properties such as a cooling / heating cycle may decrease. The multilayer coating film thus obtained is also one aspect of the present invention.

  The multilayer coating film formed by the multilayer coating film forming method of the present invention has a unique design and color development, recoat adhesion, chipping resistance, and water resistance adhesion on the surface thereof.

  In the present invention, a step of forming an uncured base coating layer by applying the above base coating composition, preferably an aqueous base coating composition, onto a substrate on which the above base coating layer is preferably formed. (1) a step (2) of applying a clear coating composition on the uncured base coating layer to form an uncured clear coating layer, and the uncured base coating layer And a multi-layer coating film forming method (so-called two-coat one-bake (2C1B) method) including the step (3) of simultaneously baking and curing the uncured clear coating film layer from the viewpoint of cost and workability. .

  The multilayer coating film formed on the substrate by the method of the present invention includes a base coating film layer and at least one clear coating film layer. An undercoating layer selected from the group consisting of intermediate coating layers may further be included. In the present invention, the base coating layer contains the interference mica pigment (A) having a dark area and the aluminum pigment (B) having an average particle diameter of 5 to 16 μm in a specific ratio, thereby obtaining a lightness L * (15 °) value is 115 or less, L * (45 °) value is 60 or more, and L * (110 °) value is 35 or less, completely different from flip-flop (FF) effect, continuous It is possible to provide a silver coating color having a brightness change.

  The multilayer coating film formed on the substrate by the method of the present invention is particularly characterized by the base coating layer formed from the base coating composition, and the above-mentioned continuous brightness change is caused by this base coating layer. In addition, a unique design called “darkness” or “just feeling” can be imparted to the coating film.

  These unconventional designs of the multi-layer coating film formed by the present invention, particularly when applied to an object to be coated in a complicated shape such as an automobile body and exposed to sunlight, particularly its highlight portion. It is very effective to make the shape of In addition, since the multilayer coating film formed by the present invention has a “darkness” or “motivated feeling”, it can also highlight shade portions that are not exposed to strong light, and can be uneven even indoors. The formation of a certain object can be emphasized.

  Furthermore, the coating color of the multilayer coating film formed according to the present invention is different from the so-called gray metallic coating film containing conventional carbon black and titanium, and its coating color and atmosphere are completely different from those of the conventional gray metallic coating. There is no crisp impression (smooth feeling, sensation of feeling) or yellowness based on carbon black or titanium, and according to the present invention, a “dark feeling” provides a sense of depth and luxury.

  Hereinafter, the present invention will be described in more detail with reference to production examples, examples and comparative examples. “Part” in each example represents “part by mass”, and “%” represents “% by mass”.

Production Example 1 Preparation of Acrylic Resin Emulsion (Em-1) 135.4 parts of ion exchange water, Aqualon HS-10 (polyoxyethylene alkylpropenyl phenyl ether sulfate, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) 1.1 The temperature was raised to 80 ° C. with mixing and stirring in a nitrogen stream. Next, 35.73 parts of methyl acrylate, 8.57 parts of butyl methacrylate, 5.7 parts of 2-hydroxyethyl methacrylate, 20 parts of styrene, 0.5 part of Aqualon HS-10, Adeka Soap NE-20 ( α- [1-[(allyloxy) methyl] -2-nonylphenoxy] ethyl) -ω-hydroxyoxyethylene (manufactured by Asahi Denka Co., Ltd., 80% aqueous solution) 0.5 part and ion-exchanged water 49.7 parts A first-stage ethylenically unsaturated monomer mixture and an initiator solution consisting of 0.21 part of ammonium persulfate and 8.6 parts of ion-exchanged water were dropped into the reaction vessel in parallel over 2 hours. After completion of the dropping, aging was performed at the same temperature for 1 hour.

  Furthermore, 25.3 parts of butyl methacrylate, 2.4 parts of 2-hydroxyethyl methacrylate, 2.3 parts of methacrylic acid, 0.1 part of Aqualon HS-10 and 24.7 parts of ion-exchanged water were added to this reaction vessel. A second stage ethylenically unsaturated monomer mixture and an initiator solution consisting of 0.08 parts ammonium persulfate and 7.4 parts ion-exchanged water were added dropwise in parallel over 0.5 hours at 80 ° C. . After completion of the dropping, aging was performed at the same temperature for 2 hours.

  Next, after cooling to 40 ° C. and filtering with a 400 mesh filter, 2.14 parts of ion-exchanged water and 0.24 part of dimethylaminoethanol were added to adjust the pH to 6.5, an average particle diameter of 80 nm, and a non-volatile content of 30%. An acrylic resin emulsion (Em-1) having a solid content acid value of 15 and a hydroxyl value of 35 was obtained.

Production Example 2: Preparation of water-soluble acrylic resin 23.89 parts of dipropylene glycol methyl ether and 16.11 parts of propylene glycol methyl ether were added to a reaction vessel, and the mixture was heated to 105 ° C. with mixing and stirring in a nitrogen stream. Next, 13.1 parts of methyl methacrylate, 68.4 parts of ethyl acrylate, 11.6 parts of 2-hydroxyethyl methacrylate, 6.9 parts of methacrylic acid, 10.0 parts of dipropylene glycol methyl ether and t-butyl An initiator solution consisting of 1 part of peroxy 2-ethylhexanoate was dropped into the reaction vessel in parallel over 3 hours. After completion of the dropping, aging was performed at the same temperature for 0.5 hours.

  Next, an initiator solution consisting of 5.0 parts of dipropylene glycol methyl ether and 0.3 part of t-butylperoxy 2-ethylhexanoate was dropped into the reaction vessel over 0.5 hours. After completion of the dropping, aging was performed at the same temperature for 2 hours.

  Further, using a solvent removal apparatus, 16.11 parts of the solvent was distilled off at 110 ° C. under reduced pressure (70 torr), and then 204 parts of ion-exchanged water and 7.1 parts of dimethylethanolamine were added to obtain a water-soluble acrylic resin. It was. The obtained acrylic resin solution had a non-volatile content of 30.0%, a solid content acid value of 40 mgKOH / g, and a hydroxyl value of 50 mgKOH / g.

Production Example 3: Preparation of Hydrophobic Melamine Resin Water Dispersion (MFD-1 ) 50 parts of MFDG (methylpropylene diglycol, manufactured by Nippon Emulsifier Co., Ltd.) was added to the reaction vessel, and the temperature was raised to 130 ° C. while stirring in a nitrogen stream. Warm up. Next, an ethylenic polymer consisting of 14.77 parts of acrylic acid, 32.48 parts of 2-hydroxyethyl methacrylate, 47.75 parts of butyl acrylate, and 5 parts of MSD-100 (α-methylstyrene dimer, Mitsui Chemicals). A saturated monomer mixture and an initiator solution consisting of 13 parts of Kayaester O (tert-butyl peroctanoate, manufactured by Kayaku Akzo) and 10 parts of MFDG were dropped into the reaction vessel in parallel over 3 hours. After the completion of dropping, an initiator solution consisting of 0.5 parts of Kayaester O and 5 parts of MFDG was added dropwise over 0.5 hours. After completion of the dropwise addition, aging was performed at the same temperature for 1 hour. Subsequently, it was cooled to 50 ° C. to obtain an acrylic resin (Ac1) having a nonvolatile content of 60%, a solid content acid value of 110 mgKOH / g, a hydroxyl value of 140 mgKOH / g, and a number average molecular weight (Mn) = 3000.

  178.5 parts of the obtained acrylic resin (Ac1) was mixed with 800 parts of Uban 20SB (fully butylated melamine resin, Nippon Cytec Co., Ltd., nonvolatile content 75%) and stirred at 80 ° C. for 4 hours. Thereafter, 18.3 parts of dimethylethanolamine was added and dispersed uniformly. After cooling to 40 ° C., 1003.2 parts of ion-exchanged water was added dropwise over 1 hour, whereby a hydrophobic melamine resin aqueous dispersion (MFD-1) was added. ) The particle size of the resin particles in this aqueous dispersion was 80 nm.

Production Example 4: Preparation of Base Coating Composition (1) 153.3 parts of the acrylic resin emulsion (Em-1) of Production Example 1 as a film-forming resin, 5 parts of a 10% by weight dimethylethanolamine aqueous solution, Production Example 2 16.7 parts of a water-soluble acrylic resin, 10 parts of Primepol PX-1000 (bifunctional polyether polyol, Sanyo Chemical Industries, Ltd., number average molecular weight 1000, hydroxyl value 278), hydrophobic melamine resin dispersion of Production Example 3 100 parts of the body (MFD-1), 3.67 parts (reduced mica) (manufactured by Shiseido Co.) as the pigment (A), 3.67 parts (PWC = 3% by mass), and the aluminum pigment as the pigment (B) (Made by Asahi Kasei Co., Ltd., trade name MH8801) (average particle size 5 to 16 μm) 8.56 parts (PWC = 7% by mass) was blended (mass ratio A). B = 3/7). Further, 30 parts of ethylene glycol monohexyl ether was mixed and stirred, adjusted to pH = 8.5 by adding 10% by mass aqueous dimethylaminoethanol solution, and uniformly dispersed to obtain an aqueous base coating composition. The resulting aqueous base coating composition has a coating viscosity of 20 ° C. The base coating composition (1) used for coating was obtained by adding ion-exchanged water and diluting it so that it would be 60 seconds in a 4 Ford cup.

Production Example 5: Preparation of Base Coating Composition (2) According to Production Example 4, instead of pigment (B) used in Production Example 4, an aluminum pigment (trade name 93-0647 manufactured by Toyo Aluminum Co., Ltd.) (average particle diameter) 5-21 μm) was mixed with 8.56 parts (PWC = 7% by mass) to obtain a comparative base coating composition (2).

Production Example 6: Preparation of Base Coating Composition (3) According to Production Example 4, instead of pigment (A) used in Production Example 4, titanium pigment (trade name CR-97, manufactured by Ishihara Sangyo Co., Ltd.) (average particle diameter) 0.10 to 0.25 μm) was blended with 3.67 parts (PWC = 3% by mass) to obtain a comparative base coating composition (3).

Production Example 7: Preparation of Base Coating Composition (4) According to Production Example 4, instead of the pigment (A) used in Production Example 4, a titanium oxide mica pigment having no dark area (Merck, trade name) A base coating composition (4) for comparison was obtained by blending 3.67 parts (PWC = 3 mass%) of T60-23WNT Galaxy Blue (average particle size 5 to 30 μm).

Production Example 8: Preparation of Base Coating Composition (5) According to Production Example 4, without using the pigment (A) used in Production Example 4, only 12.74 parts (PWC = 7% by mass) of Pigment (B) ) To obtain a comparative base coating composition (5).

Production Example 9: Preparation of Base Coating Composition (6) According to Production Example 4, only 12.22 parts (PWC = 10% by mass) of pigment (A) used in Production Example 4 was used, and pigment (B) was blended. Thus, a comparative base coating composition (6) was obtained.

Production Example 10: Preparation of Base Coating Composition (7) According to Production Example 4, instead of pigment (A) used in Production Example 4, carbon black (trade name R-5000, manufactured by Columbia Carbon Co.) (average particle size) 0.01 to 0.09 μm) was blended in an amount of 0.84 parts (PWC = 0.7% by mass) to obtain a comparative base coating composition (7).

Production Example 11: Preparation of Base Coating Composition (8) According to Production Example 4, 1.22 parts (PWC = 1% by mass) of pigment (A) used in Production Example 4 was blended, and Pigment (B) A base coating composition (8) for comparison was obtained by blending 0 part (PWC = 9% by mass) (mass ratio A / B = 1/9).

Production Example 12: Preparation of Base Coating Composition (9) According to Production Example 4, 6.11 parts (PWC = 5% by mass) of pigment (A) used in Production Example 4 was blended, and Pigment (B) was 6. 11 parts (PWC = 5 mass%) was blended to obtain a comparative base coating composition (9) (mass ratio A / B = 5/5).

Example 1
Dull steel plates (length 300 mm, width 100 mm and thickness 0.8 mm) were subjected to chemical conversion treatment using a zinc phosphate treatment agent ("Surfdyne SD2000", manufactured by Nippon Paint Co., Ltd.), followed by cationic electrodeposition coating ("Power Nix PN 310 ”(manufactured by Nippon Paint Co., Ltd.) was electrodeposited so that the dry film thickness was 25 μm. Next, after baking at 160 ° C. for 30 minutes, as an intermediate coating material, a polyester / melamine gray intermediate coating material (“Olga P-30”, manufactured by Nippon Paint Co., Ltd.) ethyl acetate / solvesso 100 / butyl diglycol acetate = 1 / 1/1 (weight ratio), Ford Cup No. 4 was adjusted so that the viscosity was 30 seconds, and the intermediate coating was performed using a rotary electrostatic coating machine, and baked and dried at 140 ° C. for 30 minutes. The intermediate coating film with an average dry film thickness of 30 μm A layer was formed.
Furthermore, the base coating composition (1) prepared in Production Example 4 was spray-coated on the intermediate coating layer so that the average dry film thickness was 15 μm. The coating was performed using an electrostatic coating machine (“Auto REA”, manufactured by ABB Industry) at an atomization pressure of 2.0 kg / cm ² . The booth atmosphere during painting was maintained at a temperature of 25 ° C. and a humidity of 75%. After coating, set for 3 minutes, preheat at 80 ° C. for 5 minutes, and then wet-on-wet on top of the acrylic / melamine resin-based clear coating composition (acid epoxy curable acrylic resin-based clear coating composition (“Mac Flow O -1810 ”(manufactured by Nippon Paint Co., Ltd.) was spray-coated to a dry film thickness of 35 μm, set at room temperature for 7 minutes, and baked at 140 ° C. for 30 minutes to form a multilayer coating film (2 coats) 1 bake (2C1B)).

Comparative Example 1
In place of the base coating composition (1) prepared in Production Example 4 in Example 1, a comparative base coating composition (2) prepared in Production Example 5 was used, and a multilayer coating was applied according to Example 1. A film was formed.

Comparative Example 2
In place of the base coating composition (1) prepared in Production Example 4 in Example 1, the comparative base coating composition (3) prepared in Production Example 6 was used and multilayer coating was performed according to Example 1. A film was formed.

Comparative Example 3
In place of the base coating composition (1) prepared in Production Example 4 in Example 1, the comparative base coating composition (4) prepared in Production Example 7 was used and multilayer coating was performed according to Example 1. A film was formed.

Comparative Example 4
In place of the base coating composition (1) prepared in Production Example 4 in Example 1, a comparative base coating composition (5) prepared in Production Example 8 was used, and a multilayer coating was applied according to Example 1. A film was formed.

Comparative Example 5
In place of the base coating composition (1) prepared in Production Example 4 in Example 1, a comparative base coating composition (6) prepared in Production Example 9 was used, and a multilayer coating was applied according to Example 1. A film was formed.

Comparative Example 6
In place of the base coating composition (1) prepared in Production Example 4 in Example 1, a comparative base coating composition (7) prepared in Production Example 10 was used, and a multilayer coating was applied according to Example 1. A film was formed.

Comparative Example 7
In place of the base coating composition (1) prepared in Production Example 4 in Example 1, a comparative base coating composition (8) prepared in Production Example 11 was used, and multilayer coating was performed according to Example 1. A film was formed.

Comparative Example 8
In place of the base coating composition (1) prepared in Production Example 4 in Example 1, the comparative base coating composition (9) prepared in Production Example 12 was used and multilayer coating was performed according to Example 1. A film was formed.

  Moreover, the brightness | luminance (L * value) measured with the multilayer coating film formed in the Example and the comparative example is shown in the following tables. The lightness (L * value) was measured using a multi-angle spectrophotometer “MA-68II” manufactured by Xrite, as shown in FIG. The lightness at the positions of 15 ° (highlight portion), 45 ° (intermediate) and 110 ° (shade portion), ie 15 ° lightness (L * (15 °) value), with the reflected position as the reference (0 °) , 45 degree lightness (L * (45 °) value) and 110 degree lightness (L * (110 °) value) were measured respectively.

  The results are shown in the table below.

Visual particle feeling The particle feeling of the pigment contained in the multilayer coating film formed in Examples and Comparative Examples was visually observed and evaluated in the following 1 to 5 stages.
Evaluation Criteria 1: It looks as if there are no black particles or only white particles.
2: There are almost no black particles, and it appears as if white particles are clearly present.
3: Looks like a small amount of black particles are present or white particles are also mixed.
4: Black particles are present, but it appears as if a small amount of white particles are also present.
5: It looks as if only black particles are present.

Darkness / Feeling of a feeling (black particle feeling)
The multilayer coating films formed in Examples and Comparative Examples were visually observed and evaluated according to the following criteria.
○: Darkness / feeling of blackness (black particle feeling).
X: Darkness / no feeling (black particle feeling).

  In Example 1, the base coating film contains an interference mica pigment (A) having a dark region and an aluminum pigment (B) having an average particle diameter of 5 to 16 μm, the total content concentration (PWC) = 10% by mass, It is characterized by including by mass ratio (A / B) = 3/7. In the coating film of Example 1, the 15-degree lightness (L * (15 °) value) is 110.0. At this time, the so-called highlight portion shows a silver coating color. Further, the coating film of Example 1 has a lightness of 110 degrees (L * (110 °) value) of 32.4. At this time, the so-called shade portion has the strongest black particle feeling. "Feeling / feeling finally" appears clearly. Here, “darkness / motivation” means that the black particles appear to be scattered in three dimensions, and the aluminum pigment particles not only in the shade part but also in the highlight part. The glittering feeling (metallic particle feeling) based on feeling can be suppressed. Moreover, in the coating film of Example 1, 45 degree lightness (L * (45 degree) value) of the intermediate part of a highlight part and a shade part is 63.5, and lightness is gentle from a highlight part to a shade part. It changes continuously. Therefore, in the coating film of Example 1, the brightness does not change abruptly unlike the flip-flop (FF) effect using the conventional metallic glitter material.

  In Comparative Example 1, since the conventional aluminum pigment having an average particle diameter of 5 to 21 μm is used without using the aluminum pigment (B) having an average particle diameter of 5 to 16 μm, the lightness of 45 degrees (L * (45 ° ) Value) is 45.5, indicating a bright silver coating color, but the white particles of aluminum itself become stronger and the glare feel becomes stronger. Further, in the coating film of Comparative Example 1, there is no “dark feeling / motivated feeling” (black particle feeling) even though the same pigment (A) as in Example 1 is used in the same amount.

  In Comparative Example 2, a titanium pigment is blended instead of the pigment (A) used in Example 1. Moreover, the coating film of the comparative example 2 has the same pigment (B) as Example 1 in the same quantity. However, in the coating film of Comparative Example 2, the lightness at 110 degrees (L * (110 °) value) is 53.6, and a coating film with a soft coating color called so-called titanium gray metallic is formed. In the comparative example 2, the so-called shade portion becomes bright and yellowish because it contains titanium. Moreover, in the coating film of the comparative example 2, the white particle feeling of aluminum and a titanium pigment becomes strong, and "a feeling of darkness / a feeling of feeling" (black particle feeling) like Example 1 cannot be observed.

  In Comparative Example 3, in place of the pigment (A) used in Example 1, a conventional titanium oxide mica pigment having no dark area is blended. The coating film of Comparative Example 3 contains the same pigment (B) as in Example 1 in the same amount. However, in the coating film of Comparative Example 3, the lightness at 110 degrees (L * (110 °) value) is 40.7, and the lightness at the shade portion is increased. "(Black particle feeling) is not obtained, and the coating film has a smooth coating color.

  In Comparative Example 4, only the pigment (B) used in Example 1 is used, and no other pigment is contained. As a result, the 15-degree lightness (L * (15 °) value) is 118.4, the 110-degree lightness (L * (110 °) value) is 39.7, and a so-called conventional silver metallic paint film is formed. Is done. Further, in Comparative Example 4, the “dark feeling / just feeling” (black particle feeling) as in Example 1 cannot be obtained.

  In Comparative Example 5, only the pigment (A) used in Example 1 is used, and no other pigment is contained. As a result, the 15-degree lightness (L * (15 °) value) is 32.0, the 45-degree lightness (L * (45 °) value) is 16.2, and the 110-degree lightness (L * (110 °) value). ) Becomes 5.6, and only a black coating film is formed. Further, in Comparative Example 5, the pigment particle feeling is strong, and the “dark feeling / motivated feeling” (black particle feeling) as in Example 1 cannot be obtained.

  In Comparative Example 6, carbon black is blended instead of the pigment (A) used in Example 1, and the same pigment (B) as in Example 1 is blended in the same amount. As a result, the lightness at 110 degrees (L * (110 °) value) is 38.8, and a conventional gray metallic paint film is formed. Moreover, since the coating film of the comparative example 6 contains carbon black, a coating film becomes yellowish. Further, the coating film of Comparative Example 6 does not have the “dark feeling / motivated feeling” (black particle feeling) as in Example 1.

  In Comparative Example 7, the same pigments (A) and (B) as used in Example 1 are used, but the mass ratio (A / B) is 1/9, and as a result, the brightness of 15 degrees (L * (15 °) value) is 121.5, and a silver coating color is obtained, but the “dark feeling / motivated feeling” (black particle feeling) as in Example 1 is not obtained.

  In Comparative Example 8, the same pigments (A) and (B) used in Example 1 are used, but the mass ratio (A / B) is 5/5, and as a result, the lightness of 45 degrees (L * (45 °) value) becomes 56.0, and the brightness change becomes large, and the “dark feeling / motivated feeling” (black particle feeling) as in Example 1 cannot be obtained.

In the method of the present invention, by forming a base coating layer containing an interference mica pigment (A) having a dark region and an aluminum pigment (B) having an average particle diameter of 5 to 16 μm in a specific blending amount and ratio. Continuous brightness change (lightness L * (15 °) value is 115 or less, L * (45 °), which is different from the flip-flop (FF) effect of a metallic coating film using a conventional metallic glitter material) A silver paint film having a value of 60 or more and an L * (110 °) value of 35 or less can be formed. In addition, the multilayer coating film formed by the method of the present invention increases the contrast between the brightness (L * (15 °) value) of the highlight portion and the brightness (L * (110 °) value) of the shade portion. Furthermore, it is possible to give a unique “feel of darkness / at last” (black particle feeling) to the silver paint color. Thereby, a unique design can be given to the coating film. In particular, in the coating film of the present invention, in a portion that is often exposed to light, which is called a highlight portion, a “feel of darkness / motivation” (black particle sensation) causes a glare sensation (whiteness) based on the particles of the metallic glitter material. ) Can be suppressed, and the modeling at the highlight part of the object can be seen well. Further, in a portion where light called a shade portion does not hit well, the shadow becomes stronger due to the “darkness / momentality” (black particle feeling), and the contrast with the highlight portion can be further enhanced. Furthermore, the coating film of the present invention can give a feeling of depth and depth to the coating film by “darkness / motivation” (black particle feeling), and can give a high-class feeling to the silver coating color. . In addition, as described above, the multilayer coating film formed by the method of the present invention has a black particle feeling and does not have a glare feeling (particle feeling) based on the particles of the conventional metallic glitter material. There is no silver metallic color.
Therefore, the method of the present invention is particularly useful when applied to an object to be coated having a complicated shape having unevenness such as an automobile body and whose design is very important as a product.

  In addition, the painting method of the present invention can be applied not only to the automobile body, but also to all articles and products that require painting, such as the bodies of vehicles such as motorcycles and tricycles, and their parts, containers, and electrical appliances. It can be applied to any painting field.

1 Painted object 2 Highlight part 3 Shade part 4 Intermediate part 5 Incident light

Claims (3)

On the substrate, a base coating layer containing an interference mica pigment (A) having a dark region and an aluminum pigment (B) having an average particle diameter of 5 to 16 μm is formed, and further a clear coating layer is formed. Formation of a multi-layer coating film having a silver coating color with an L * (15 °) value of 115 or less, an L * (45 °) value of 60 or more, and an L * (110 °) value of 35 or less A method,
The concentration (PWC) of the total content of the interference mica pigment (A) having the dark area and the aluminum pigment (B) is 5 to 15% by mass, and
The mass ratio (A / B) of the interference mica pigment (A) having the dark area and the aluminum pigment (B) is 2/8 to 4/6.
A method for forming a multilayer coating film.   The formation method of the multilayer coating film of Claim 1 whose average particle diameter of the interference mica pigment (A) which has the said dark part area | region is 5-25 micrometers.   The multilayer coating film obtained by the formation method of the multilayer coating film of Claim 1 or 2.

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