JP7352397B2 - Method for forming multilayer coating film with retroreflectivity - Google Patents

Description

The present invention relates to a method for forming a multilayer coating film that has both a luxurious and profound design and retroreflectivity.

Retroreflection is a special optical reflection mechanism in which incident light returns to the direction of incidence. Unlike specular reflection, where the incident angle and reflection angle are equal, the received light is reflected directly back to the light source, which has the effect of increasing visibility from the direction of the light source, so it is used for traffic signs, reflective displays on vehicles, etc. There is.

In order to obtain a laminated structure that exhibits retroreflectivity, it has been known to form this retroreflective structure by a coating method. For example, in Patent Document 1, on a road wheel base material in which the base coating layer is formed of a powder coating, a metallic coating layer containing a glittering pigment made into metal fragments by crushing a vapor-deposited metal film, and glass beads are provided. A method for forming a glittering coating film is disclosed, in which a coating layer containing a clear coating layer and a clear coating layer are sequentially formed. Painted retroreflective structures are relatively inexpensive and can be easily painted into any shape, but in order to obtain sufficient retroreflectivity, the reflective layer requires a highly reflective metallic coating layer and glass beads are densely placed on top of it. It was necessary to cover the area. That is, it has been common for the retroreflective layer to contain glass beads as a retroreflective material at a high concentration, for example, 80% by weight or more. Metallic coatings usually have a sharp change in brightness depending on the angle (normally, a high value of L* ₁₅ /L* ₇₅ with high flip-flop property is considered to be good), and the reflective layer is a metallic coating layer. In some cases, there is a large difference in brightness depending on the angle, and the resulting multilayer coating film has noticeable glare and unevenness when viewed from a certain angle, and there have been problems in imparting a high-class design.

On the other hand, among metallic designs, for example, paint colors such as gun metallic color (black iron color with a gun-like luster) are one of the most popular paint colors because of their profound feeling. Gun metallic color has a design with lower brightness than general silver metallic color, and it is a paint color that is difficult to control unevenness.

For example, Patent Document 2 discloses a method for forming a coating film with a silver metallic color having low brightness, in which a bright coating composition containing an aluminum flake pigment and an interference mica pigment having a dark area in a specific ratio is used as a base coat. A method for forming a coating film is disclosed in which a top coat layer is formed using a clear paint after forming a layer. Even when the hue of the coating film is dark, it emits interference colors and can obtain a deep color tone without causing a white blur in the shaded area.

However, when a bead layer is further formed as a retroreflective layer on such a base coat layer, due to the unique optical properties of the beads, there is a yellowish or milky whitish feeling in the shade area (diagonal direction), and it is difficult to see from all angles. When viewed, there was a problem that the interference color was uneven and it did not look like a beautiful gunmetal. In addition, compared to forming a normal metallic coating film on the reflective layer, gunmetal color aims to create a design with low brightness, so some of the incident light is absorbed and the overall brightness tends to be low. Difficult to obtain retroreflectivity. Furthermore, when a colored pigment such as carbon black is used to lower the brightness, the retroreflected light may take on a yellowish tinge, making it impossible to obtain a beautiful gunmetal design.

Japanese Patent Application Publication No. 2001-79485 Japanese Patent Application Publication No. 2001-16419

When viewed from all angles, the coating has a shiny metallic appearance with a solid feel, exhibits sufficient retroreflectivity with high brightness at night, and has a luxurious and dignified design that combines functionality. To provide a method for forming a multilayer coating film having retroreflectivity, which can obtain the following properties.

As a result of intensive studies to solve the above problems, the present inventors have developed a method for forming a multilayer coating film having retroreflectivity, in which an aluminum pigment and/or an interference pigment are added as a glittering pigment in a specific ratio to a reflective layer. By using the base paint composition contained in the paint composition to keep the L value below a specific value, a shiny metallic design with a more profound and luxurious feel is created, and when viewed from all angles, especially in the shade area, it has high brightness. It was discovered that a multilayer coating film having retroreflectivity could be obtained, and the present invention was achieved.

That is, the present invention includes the following aspects.

Item 1. Step (1) of coating a base coating composition containing an aluminum pigment (a1) and/or an interference pigment (a2) as a glittering pigment onto an object to be coated to form a metallic base coating layer (I) as a reflective layer. ),
Step (2) of coating a retroreflective coating composition containing high refractive index beads to form a retroreflective coating layer (II), then coating at least one layer of a clear coating composition to form a clear coating layer (III); ) forming step (3);
A method for forming a multilayer coating film comprising in this order, the formation of a multilayer coating film having retroreflectivity, characterized in that the L*45 value of the metallic base coating layer (I) is 50 or less. Method.

Item 2. The total content of the aluminum pigment (a1) and the interference pigment (a2) in the base coating composition is within the range of 5 to 20 parts by weight, based on 100 parts by weight of the resin solid content of the base coating composition. 1. The method for forming a multilayer coating film having retroreflectivity as described in 1.

Item 3. The compound having retroreflectivity according to item 1 or 2, wherein the mass ratio of the aluminum pigment (a1) and the interference pigment (a2) is within the range of (a1/a2) = 20/80 to 50/50. Method of forming layer coatings.

Item 4. Any one of Items 1 to 3, wherein in step (2), a retroreflective coating composition is spray-coated onto an uncured base coating to form a retroreflective coating layer (II). A method for forming a multilayer coating film having retroreflectivity as described in 2.

The resulting multi-layer coating has a shiny metallic appearance with a solid feeling when viewed from all directions with little angle dependence, and has high light retroreflectivity even when it is a gunmetal color with relatively low brightness at night. It is possible to obtain a coating film that has both design and functionality.

In addition, since the base coating layer (I) and the retroreflective coating layer (II) have excellent adhesion, it is possible to apply the topcoat without causing the high refractive index beads to fall off, and the clear topcoat It also has excellent adhesion to the membrane layer (III).

An example of the coating film structure of the present invention and an image diagram of gloss distribution and retroreflected light depending on the angle of change.

<<Method for forming multilayer coating film with retroreflectivity>>
The method for forming a multilayer coating film having retroreflective properties according to the present invention includes coating a base coating composition containing an aluminum pigment (a1) and/or an interference pigment (a2) on an object to be coated to form a metallic base coating film. Step (1) of forming layer (I) as a reflective layer;
Step (2) of coating a retroreflective coating composition containing high refractive index beads to form a retroreflective coating layer (II), then coating at least one layer of a clear coating composition to form a clear coating layer (III); ) A method for forming a multilayer coating film comprising a step (3) of forming
The metallic base coating layer (I) is characterized in that the L*45 value is 50 or less.

<Object to be coated>
The object to be coated is not particularly limited, and it is useful for articles such as exteriors and interiors of buildings, structures, vehicles, electrical appliances, etc. For example, the bodies of railway vehicles, aircraft, ships, automobiles, motorcycles, bicycles, tricycles, unicycles, etc. or their parts; road surrounding materials such as soundproof walls, tunnel interior boards, guardrails; siding materials, tiles, glass, sashes, screen doors, Housing-related parts such as gates, carports, sunrooms, balcony parts, roof parts, housing exterior wall parts, bathroom mirrors, bathroom walls, bathtubs, cosmetic mirrors, sanitary ware, etc.; show windows, refrigerated product cases, frozen product cases, etc. Store-related parts; household electrical appliances such as mobile phones, audio equipment, personal computers, etc. can be mentioned.

There are no particular restrictions on the material of the base material of these objects to be coated, and examples include iron, aluminum, brass, copper, stainless steel, tinplate, galvanized steel, and alloyed zinc (Zn-Al, Zn-Ni, Zn -Fe, etc.) Metal materials such as plated steel; resins such as polyethylene resin, polypropylene resin, acrylonitrile-butadiene-styrene (ABS) resin, polyamide resin, acrylic resin, vinylidene chloride resin, polycarbonate resin, polyurethane resin, epoxy resin, etc. Examples include plastic materials such as FRP; inorganic materials such as glass, cement, and concrete; wood; and fibrous materials (paper, cloth, etc.). Among these, at least one selected from metal materials and plastic materials is suitable. These materials may be in the form of a flat plate or may be processed and molded into a desired shape.

An undercoat, intermediate coat, colored base coating, etc. may be formed on the object to be coated, and the coating color is not particularly limited.

<Step (1) of forming the metallic base coating layer (I) as a reflective layer>
The method for forming a multilayer coating film of the present invention is a step of coating a base coating composition containing an aluminum pigment (a1) and/or an interference pigment (a2) to form a metallic base coating layer (I) as a reflective layer. (1), and the L*45 value of the metallic base coating layer (I) is 50 or less.

A metallic base paint composition is a paint composition that contains a bright glittering pigment, a vehicle-forming resin composition, and paint additives as necessary, as materials that can create a design with a glittering metallic feel. It is a thing.

A metallic base coating film as the metallic base coating layer (I) is formed by applying a metallic base coating composition and finally heating and drying to form a cured coating film. The cured thickness of the metallic base coating is preferably 5 to 40 μm, preferably 8 to 30 μm, and more preferably 10 to 20 μm from the viewpoint of achieving both design and retroreflectivity.

In addition, in the present invention, the L* value is calculated by emitting light from an angle of 45° to the axis perpendicular to the surface to be measured using a multi-angle spectrophotometer, and measuring the reflected light perpendicular to the surface to be measured. These are the values when L*, a*, b* (JIS Z 8729 (2004)) are measured for light in a direction (light received at an angle of 45° with respect to specularly reflected light). As the multi-angle spectrophotometer, for example, "CM-512m3" (trade name, manufactured by Konica Minolta), "MA-68II" (trade name, manufactured by X-Rite), etc. can be used. In this specification, the L*45 value measured using the MA-68II with a cured coating film of 15 μm is used as a reference.

A metallic base coating layer with an L*45 value of 50 or less, preferably 1 to 45, can be obtained by adjusting the pigment components of the base coating composition. From the viewpoint of achieving both properties, it is essential to use an aluminum pigment (a1) and/or an interference pigment (a2) as the bright pigment. From the viewpoint of achieving a design with a strong and profound metallic feel, preferably the aluminum pigment (a1) is essential, and from the viewpoint of design and brighter retroreflectivity, the aluminum pigment (a1) and the light interference pigment ( It is preferable to use a2) in combination.
Aluminum pigment (a1)
Aluminum pigment is a pigment that contains aluminum, and is used to hide the base layer under the metallic base coating, to obtain a coating with excellent glittering metallic luster, and to obtain sufficient retroreflectivity. used for.

The shape of the aluminum pigment may be coin-like, flake-like, or scale-like, and the average particle diameter (D50) is preferably about 5 to 100 μm, more preferably about 6 to 35 μm. The above average particle diameter means the major axis (size in the longitudinal direction). The thickness is about 0.001 to 2 μm, more preferably about 0.05 to 1 μm. Specific examples of aluminum pigments include aluminum flake pigments and vapor-deposited aluminum flake pigments.

Aluminum flake pigments are flake-like pigments based on aluminum.

The vapor-deposited aluminum flake pigment is obtained by vapor-depositing an aluminum film on a base material, peeling off the base material, and then pulverizing the vapor-deposited aluminum film. Examples of the base material include a film.

In particular, it is preferable to use an aluminum pigment with high brightness (also referred to as high brightness), and the IV value of the coating film containing the aluminum pigment is in the range of 100 to 550, more preferably 200 to 350. It is preferable to do so from the viewpoint of a balance between a profound design and good retroreflectivity.

The IV value is an abbreviation for Intensity Value, and is a numerical value that indicates the brightness in a highlight, and the smaller the value, the darker it is, and the higher the value, the brighter it feels.

In this specification, the IV value of a paint film containing aluminum pigment is defined as a value measured using "Alcope LMR-200H" manufactured by Kansai Paint Co., Ltd., of a paint film painted under specified conditions. do. Further, in this specification, the IV value is a special value indicating the brightness of the aluminum pigment.

As the aluminum pigment, either an aluminum flake pigment or a vapor-deposited aluminum flake pigment can be used, or both can be used.

Further, the aluminum pigment may be surface-treated with silica, resin, or the like.

The aluminum pigments are roughly classified into two types, leafing and non-leafing, depending on their orientation behavior in the coating film, and either one or both can be used.

Generally, the smaller the average particle diameter of the aluminum pigment, the higher the coating hiding ability. The larger the average particle diameter, the better the sparkle feeling (glitter feeling). As aluminum pigments, those with an average particle diameter (D50) in the range of 6 to 14 μm are considered small particle diameters, those in the range of 15 to 22 μm are medium particle diameters, and those in the range of more than 22 μm to 100 μm are considered large particle diameters. , these may be used alone or in combination.

Interference pigment (a2)
When the interference pigment (a2) is contained, the interference light and transmitted light expressed by the interference pigment (a2) are mixed with the reflected light peculiar to the high refractive index beads, thereby improving the brightness and improving the brightness of the base coating film. It is particularly preferred because it has the effect of adjusting the color tone and improving retroreflectivity without impairing the profound design.

Interference colors are caused by the phenomenon that when light is reflected from a certain material, a phase difference occurs in the reflected light, and specific wavelengths are strengthened or weakened. Pigments that have this effect are called interference pigments. They are sometimes called pearlescent pigments or pearlescent pigments, but they include these.

Specifically, for example, various metal oxides such as natural mica, artificial mica, glass, iron oxide, aluminum oxide (excluding those classified as aluminum pigments (a1) above or extender pigments described below), titanium oxide, etc. Examples include transparent or translucent flake-like light interference pigments. These may be used alone or in combination of two or more.

Natural mica is a scaly base material made from crushed mica ore.

Artificial mica (sometimes called synthetic mica) is a compound containing potassium, sodium, magnesium, aluminum, silicon, fluorine, etc., such as SiO ₂ , MgO, Al ₂ O ₃ , K ₂ SiF ₆ , Na ₂ SiF It is a phyllosilicate mineral obtained by mixing industrial raw materials such as No. ₆ at a certain ratio, heating the mixture, melting and crystallizing at a high temperature of about 1500°C, cooling, and then mechanically crushing. For example, something like this:
KMg ₃ (AlSi ₃ O ₁₀ )F ₂ : potassium fluorine phlogopite,
KMg _2.1/2 (Si ₄ O ₁₀ )F ₂ : Potassium tetrasilicon mica,
_KMg2Li ( _Si4O10 ) _F2 : Potassium taeniolite _,
NaMg3 ( _AlSi3O10 ) _F2 : sodium phlogopite _,
NaMg2Li ( _Si4O10 ) _F2 : sodium taeniolite _,
NaMg _2.1/2 (Si ₄ O ₁₀ )F ₂ : sodium tetrasilicon mica,
Na _1/3 Mg _2.2/3 Li _1/3 (Si ₄ O ₁₀ ) F ₂ : Sodium hectorite,
LiMg ₂ LiSi ₄ O ₁₀ F ₂ : lithium teniolite,
Examples include. When compared to natural mica, artificial mica has fewer impurities and is more uniform in size and thickness.

From the viewpoint of obtaining retroreflected light with high transparency and brightness, metal oxide-coated mica and/or metal oxide-coated glass flakes are preferred, and titanium oxide-coated synthetic mica is particularly preferred. The mica coated in the metal oxide coated mica may be either natural or synthetic.

It is a pigment that has a layer structure of at least one layer, which is made by coating mica, glass flakes, etc. with a metal oxide such as titanium oxide. Commercially available materials include metal oxide-coated mica such as titanium oxide coated interference mica pigment, metal oxide-coated alumina flakes, and metal oxide-coated glass flakes. As interference pigments, those commercially available from various companies can be used. These can be used alone or in combination of two or more.

The interference pigment (a2) may be coated with titanium oxide and then subjected to surface treatment to further improve dispersibility, water resistance, chemical resistance, weather resistance, etc.

Examples of the interference color of the interference pigment (a2) include silver, gold, red, purple, blue, and green, and the color of retroreflected light can be adjusted to a desired color to some extent. It is particularly preferable to use an interference pigment having a blue interference color from the viewpoint of providing a deeper metallic feel and alleviating the yellowness of highlights during retroreflection. In the present invention, "interference color" refers to the color tone of reflected interference light of structural coloring of an interference pigment.

Among these, when containing an interference pigment having a blue interference color, the content is 1 to 10 parts by mass based on 100 parts by mass of resin solid content of the base coating composition, from the viewpoint of retroreflectivity and design. part, preferably within the range of 2 to 8 parts by weight.

The resin solid content of the base coating composition refers to the nonvolatile content of the coating film-forming resin (vehicle-forming resin) described below.

The base coating composition may contain other pigments (a3) other than the aluminum pigment (a1) and interference pigment (a2) as pigment components within a range that does not impair the design and retroreflectivity of the present invention. It's okay.

Other pigments (a3)
Other pigment components include extender pigments, color pigments, and glitter pigments other than the aluminum pigment (a1) and interference pigment (a2).

Examples of extender pigments include clay, kaolin, barium sulfate, barium carbonate, calcium carbonate, talc, silica, and alumina white, among which barium sulfate and talc can be preferably used.

Examples of coloring pigments include titanium oxide, zinc oxide, carbon black, molybdenum red, Prussian blue, cobalt blue, azo pigments, phthalocyanine pigments, quinacridone pigments, isoindoline pigments, threne pigments, perylene pigments, Examples include dioxazine pigments and diketopyrrolopyrrole pigments, among which titanium oxide and carbon black are preferably used. In particular, as coloring pigments, in order to achieve both a profound design with lower brightness and improved retroreflectivity while suppressing yellowing, a black pigment (e.g. carbon black) and at least one coloring pigment having a complementary color relationship are used. It is preferable to use a combination of seeds (red (for example, quinacridone red) and blue (for example, phthalocyanine blue), etc.).

As other glitter pigments, for example, glitter pigments of metals such as copper, zinc, brass, and nickel, or alloys thereof can be suitably used.

These pigment components may be mixed and dispersed with a dispersant and a dispersion resin as appropriate, and the paste may be blended into a paint. Known dispersants, dispersion resins, and dispersion methods can be used.

About Content and Content Ratio The total content of pigments in the base paint composition is determined so that the L*45 value of the resulting coating film is 50 or less, from the viewpoint of a design with a profound feeling. It can be adjusted as appropriate within the range of 1 to 30 parts by mass based on 100 parts by mass of resin solid content.

In particular, the aluminum pigment (a1) in the base paint composition is used from the viewpoint of the design of the resulting multilayer coating film and the expression of retroreflectivity with high brightness when viewed from all angles, especially in the shade area. The total content of the interference pigment (a2) is preferably in the range of 5 to 20 parts by weight, more preferably in the range of 8 to 18 parts by weight, based on 100 parts by weight of the resin solid content of the base coating composition.

In addition, as for the content ratio, from the viewpoint of achieving both retroreflectivity and a profound design, the mass ratio of the aluminum pigment (a1) and the interference pigment (a2) is (a1/a2) = 10/90 ~ It is within the range of 90/10, preferably within the range of 20/80 to 50/50, particularly preferably within the range of 25/75 to 40/60.

When containing aluminum pigment (a1), the content is 0.5 to 10 parts by mass, preferably 1 to 9 parts by mass, based on 100 parts by mass of resin solid content of the base coating composition. Preferably within this range.

The content of the interference pigment (a2) is preferably 1 to 11 parts by weight, preferably 2 to 10 parts by weight, based on 100 parts by weight of the resin solid content of the base coating composition.

When other pigments are contained, their content is in the range of 1 to 27 parts by weight, preferably 2 to 10 parts by weight, based on 100 parts by weight of the resin solid content of the base coating composition.

Film-forming resin The vehicle-forming resin used in the base coating composition can contain a resin and a curing agent that are generally used as a film-forming resin (sometimes referred to as a vehicle-forming resin), such as a film-forming resin. Examples include coating film-forming resins such as acrylic resins, polyamide resins, urethane resins, polyester resins, and epoxy resins. It is preferable to use a curing agent and a resin capable of crosslinking with the curing agent as the coating film forming resin, and it is preferable to use a resin containing a hydroxyl group in order to crosslink with the curing agent. From the viewpoint of weather resistance, hydroxyl group-containing acrylic resins and/or hydroxyl group-containing polyester resins are preferred. As a curing agent, amino resins such as melamine resins, guanamine resins and urea resins, polyisocyanate compounds represented by isophorone diisocyanate (IPDI), hexamethylene diisocyanate (HMDI), etc., or their dimers or trimers; polyisocyanates. Examples include prepolymers obtained by subjecting a compound to a urethane reaction with a polyhydric alcohol, a low molecular weight polyester resin, water, etc. under conditions in which isocyanate groups are in excess. Furthermore, polyisocyanate compounds obtained by blocking the isocyanate groups with a blocking agent can also be used. Examples of the blocking agent include phenols; oximes; lactams; alcohols; mercaptans; and active methylene compounds such as diethyl malonate. When using a blocked polyisocyanate compound, it is preferable to use a dissociation catalyst for the blocking agent together. These can be used alone or in combination of two or more.

The base coating composition may further contain rheology control agents such as polymer particles, plasticizers, diluents such as organic solvents, etc. as additives within the range that does not impair transparency or design. When containing these additives, the amount is preferably 20 parts by mass or less, preferably within the range of 0.01 to 15 parts by mass, based on 100 parts by mass of resin solids in the base coating composition. .

The base coating composition can be applied by, for example, spraying using an air spray, airless spray, or rotary atomizer, and electrostatic application may be performed during the coating.

The coating thickness of the base coating film is usually within the range of 5 to 40 μm, preferably 8 to 30 μm, and more preferably 10 to 20 μm in terms of adhesiveness with the retroreflective coating layer and design. be able to.

The base coating composition may be in the form of an organic solvent-based coating composition, an aqueous or water-soluble coating composition, a solvent-free coating composition that does not substantially contain a solvent, or a powder coating composition. From the viewpoint of properties, an organic solvent-based coating composition is preferred. In addition, in this specification, an organic solvent type coating composition is a coating material that does not substantially contain water as a solvent.

At the time of coating, the base coating composition of the present invention uses a diluent as necessary to maintain a solid content of 15% by mass or more, particularly preferably within a range of 35 to 60% by mass, and a viscosity of 5 to 30 seconds. /Ford Cup #4 It is preferable to adjust the temperature within the range of 20° C. from the viewpoint of design, painting workability, and reduction of the amount of organic solvent discharged.

<Step (2) of forming retroreflective coating layer (II)>
Next, a retroreflective coating composition containing high refractive index beads is applied onto the base coating layer (I) obtained in step (1) to form a retroreflective coating layer (II).

The cured state of the base coating film (I) may be either cured or uncured, but from the viewpoint of design and retroreflectivity expression, the retroreflective coating composition is sprayed onto the uncured base coating film. Preferably, the retroreflective coating layer (II) is formed by coating.

Coating on the uncured coating film is sometimes called wet-on-wet. Wet-on-wet refers to painting in a state where the paint film is not substantially cured. "Substantially uncured state" refers to an uncured paint film, and an "uncured paint film" refers to painting in a state where the paint film is not substantially cured. This is a state that has not yet reached the hardened dry state described below, and includes the dry-to-touch state and semi-hardened dry state specified in JIS K 5600-1-1. A cured coating film is cured and dried as specified in JIS K 5600-1-1 (2004), that is, the center of the coating surface is firmly pinched between the thumb and forefinger to prevent dents from fingerprints from forming on the coating surface. This is a paint film in which no movement of the paint film is felt, and no scratches are left on the paint surface when the center of the paint surface is rubbed rapidly and repeatedly with a fingertip.

When the retroreflective coating composition of the present invention is applied to an uncured base coating, the high refractive index beads become easily embedded in the base coating layer due to the spray pressure during spray coating, and at the same time, the uncured base coating Since the bright pigment therein is easily oriented so as to surround the high refractive index beads, sufficient retroreflection can be produced, which is particularly preferable.

Examples of the retroreflective coating composition include a coating composition containing bead (spherical) particles exhibiting a high refractive index as a material capable of exhibiting a retroreflection mechanism, and a vehicle-forming resin composition. In this specification, the bead-shaped (spherical) particles exhibiting a high refractive index are hereinafter referred to as "high refractive index beads." Specifically, it refers to one with a refractive index of 1.5 or more, particularly 1.8 or more, more preferably 2.0 or more, and more preferably in the range of 2.1 to 2.3. Furthermore, from the viewpoint of retroreflection efficiency (light transmittance), glass beads are more preferably used than resin beads.

The average particle size (D50) of the high refractive index beads is preferably within the range of approximately 5 to 100 μm, more preferably within the range of 10 to 60 μm, particularly preferably within the range of 30 to 50 μm. In addition, in order to better produce the interference effect in reflected light, the particle size distribution of the high refractive index beads should be as narrow and sharp as possible, and the particle size distribution should preferably contain 80% by weight or more of particles with a particle size of 25 to 60 μm. Particularly preferably used are

The content of the high refractive index beads is not particularly limited as long as retroreflectivity can be obtained, but it is within the range of 5 to 300 parts by mass based on 100 parts by mass of the resin solid content of the vehicle-forming resin composition described below. From the viewpoint of achieving both retroreflectivity and design, the amount is preferably within the range of 10 to 150 parts by mass.

The vehicle-forming resin composition is not particularly limited, and those listed as the coating film-forming resins explained in the section of the metallic base coating layer can be used.

The retroreflective coating composition can be applied by, for example, spraying using an air spray, airless spray, or rotary atomizer, and electrostatic application may be applied during the coating.

The thickness of the retroreflective coating is usually within the range of 5 to 40 μm, preferably 10 to 30 μm, and more preferably 12 to 20 μm in terms of adhesion to the base paint layer and design. can do.

The above-mentioned retroreflective coating layer (II) itself can be heat-cured at a temperature of about 100 to 180°C, but it is also possible to form a retroreflective coating layer on an uncured base coating layer and heat-cure it at the same time. Because the high refractive index beads can be arranged in a single layer and placed very close to the glitter pigment in the base layer, the beads can be efficiently recursive while providing an excellent design with a glittery, profound feel and a luxurious feel. Reflectivity can be developed.

As preheating, preheating, air blowing, etc. may be performed. The preheating temperature is about 40 to 100°C, preferably about 50 to 90°C, more preferably about 60 to 80°C. The preheating time is about 30 seconds to 15 minutes, preferably about 1 to 10 minutes, and more preferably about 2 to 5 minutes. Further, the above-mentioned air blowing can usually be carried out by blowing air heated at room temperature or at a temperature of about 25° C. to 80° C. for about 30 seconds to 15 minutes onto the painted surface of the object to be coated.

It is preferable that the temperature of the baking treatment is usually in the range of 100 to 180°C, particularly 110 to 160°C. Further, it is preferable that the baking treatment time is usually 10 to 60 minutes.

The form of the retroreflective coating composition may be an organic solvent type, water-based or water-soluble coating, solvent-free or powder containing substantially no solvent, etc., but in terms of design and good retroreflectivity. Therefore, an organic solvent-based coating composition is preferred.

During coating, the retroreflective coating composition used in the present invention is coated with a solid content of 15% by mass or more, preferably in the range of 35 to 60% by mass, and a viscosity of 5 to 60% by mass, using a diluent as necessary. It is preferable to adjust the temperature within the range of 30 seconds/Ford Cup #4/20°C from the viewpoint of design, painting workability, and reduction of the amount of organic solvent discharged.

<Step (3) of forming clear coating layer (III)>
Next, the above-mentioned at least one clear coating layer is formed on the retroreflective coating layer (II) obtained in the above step (2).

As the clear coating composition of the present invention, conventionally known ones can be used without any restriction. For example, a liquid or powder coating composition containing a base resin and a crosslinking agent can be applied. Examples of the base resin include acrylic resins, polyester resins, alkyd resins, fluororesins, urethane resins, and silicon-containing resins containing crosslinkable functional groups such as hydroxyl groups, carboxyl groups, silanol groups, and epoxy groups. Examples of crosslinking agents include melamine resins, urea resins, polyisocyanate compounds, blocked polyisocyanate compounds, epoxy compounds or resins, carboxyl group-containing compounds or resins, acid anhydrides, and alkoxysilane group-containing compounds that can react with the functional groups of the base resin. Examples include compounds or resins. These may be used alone or in combination of two or more.

Additionally, additives such as solvents such as water and organic solvents, curing catalysts, antifoaming agents, and ultraviolet absorbers may be appropriately blended as needed. The form of the clear paint composition may be an organic solvent-based paint, a water-based or water-soluble paint, a solvent-free paint that does not substantially contain a solvent, or a powder. Coloring pigments may be included as appropriate within the range. The coloring pigment may contain one type or a combination of two or more types of pigments conventionally known for use in inks and paints. The amount added may be determined as appropriate, but is 30 parts by weight or less, preferably 0.1 to 10 parts by weight, based on 100 parts by weight of the film-forming resin composition in the clear coating composition.

The clear coating composition can be applied by, for example, spraying using an air spray, airless spray, or rotary atomizer, and electrostatic application may be applied during the coating.

The thickness of the clear coating film should preferably be applied to the extent that it covers the high refraction beads, from the viewpoint of preventing the high refraction beads from falling off, achieving uniform design, and achieving uniform retroreflection. It can be generally within the range of 5 to 60 μm, preferably 10 to 45 μm.

In the present invention, in the case where the clear paint composition is applied without heating and curing the paint film of the base paint composition and/or retroreflective paint composition, these paint films can be cured after applying the clear paint composition. may be heated and cured at the same time. The coating itself of the clear coating composition can be cured at temperatures from about 70°C to about 150°C.

With this method, the base paint composition functions as a reflective layer, and when a high refractive index bead layer is formed, it has retroreflectivity that combines a profound and luxurious design with high brightness retroreflectivity. A multilayer coating can be formed.

The multi-layer paint film with retroreflectivity obtained by the method of the present invention has a deep appearance from any angle, such as highlights and shades, even if the base paint film has a low lightness with an L*45 value of 50 or less. It has a shiny metallic appearance and exhibits sufficient retroreflectivity with high brightness at night, making it possible to obtain a coating that combines high-class design and functionality.

Hereinafter, the present invention will be explained in more detail with reference to Examples. Note that "parts" and "%" refer to "parts by mass" and "% by mass" unless otherwise specified.

In this specification, the methods for measuring various physical properties used in Examples and Comparative Examples are as follows.

(1) The number average molecular weight (Mn) was measured by gel permeation chromatography (GPC) using a standard polystyrene calibration curve. As a gel permeation chromatograph, "HLC-8120GPC" (trade name, manufactured by Tosoh Corporation) was used, and as columns, one "TSKgel G4000HXL", two "TSKgel G3000HXL", and one "TSKgel G2000HXL" were used. A total of four books (trade name, all manufactured by Tosoh Corporation) were used, and a differential refractometer was used as a detector under the conditions of mobile phase: tetrahydrofuran, measurement temperature: 40°C, and flow rate: 1 mL/min. It can be measured by

(2) Average particle size: d50 Measured using a laser micron sizer LMS-24. Mineral spirit was used as the measurement solvent. The aluminum pigment used as a sample was subjected to ultrasonic dispersion for 2 minutes as a pretreatment.

(3) Brightness Preparation of paint/coating film Add Acrylic No. 5g to aluminum pigment. 8g of 2000GL thinner (manufactured by Kansai Paint Co., Ltd.) was added and predispersed, and Acrylic No. 97 g of 2026GL Clear (manufactured by Kansai Paint Co., Ltd.) was added and shaken for 10 minutes in a paint shaker. A coating film was formed using the obtained silver metallic paint on art paper using a 9 mil applicator, and then dried at room temperature.

Next, paint research, No. 117, pp. 67-72 (1989, published by Kansai Paint Co., Ltd.), evaluation was performed using a laser type metallic feel measuring device Alcope LMR-200 (manufactured by Kansai Paint Co., Ltd.). Measurements were made under optical conditions in which a laser light source was placed at an incident angle of 45 degrees and a light receiver was placed at reception angles of 0 and -35 degrees. Of the laser reflected light, the IV value was determined at an acceptance angle of -35 degrees, which provides the maximum light intensity, excluding the light in the specular reflection area reflected on the coating surface. The IV value is a parameter proportional to the intensity of specularly reflected light from the aluminum pigment, and represents the magnitude of brightness.

Manufacturing example 1
Aluminum pigment (a1) No. 1 to 4 parts and stirred and mixed to obtain organic solvent type metallic base coating composition No. 1. 1 was adjusted.

Production examples 2 to 11
In Production Example 1, organic solvent type base coating composition No. 2 to 11 were adjusted.

Aluminum pigment No. 1: IV value = 335, average particle size 19 μm, coin-shaped aluminum pigment,
Aluminum pigment No. 2: IV value = 305, average particle size 33 μm, coin-shaped aluminum pigment,
Aluminum pigment No. 3: IV value = 180, average particle size 33 μm, flaky aluminum pigment,
Interference pigment No. 1: Gold pearl, synthetic mica, titanium oxide coated artificial pigment, median diameter D50 (μm) = approximately 21 μm, appearance white, interference color (gold),
Interference pigment No. 2: Blue pearl, synthetic mica, titanium oxide coated artificial pigment, median diameter D50 (μm) = approximately 21 μm, appearance white, interference color (blue).

Examples 1 to 9 and Comparative Examples 1 to 2
Each base paint composition No. 1 prepared as described above was applied onto a coating plate on which a gray (N-5) coating had been previously formed using a doctor blade as an object to be coated. 1~No. 11 was diluted with an organic solvent to adjust the solid content to 25% by mass, and using a small spray gun (W-101 manufactured by Anest Iwata Co., Ltd.), the booth temperature was 20 ° C., the humidity was 75%, and the discharge pressure was 2.5 kgf/cm. ^2. Painting was performed at a gun distance of 20 cm so that the cured coating film had a thickness of 10 μm. After that, it was left to stand at room temperature for 15 minutes, and then a retroreflective paint composition (Note 1) containing high refractive index beads was applied to these uncured painted surfaces (wet-on-wet) using a small spray gun (Anest Iwata Co., Ltd.). The cured coating film was coated to a film thickness of 15 μm using the company's W-101) under conditions of a booth temperature of 20° C., humidity of 75%, discharge pressure of 2.5 kgf/cm ² , and gun distance of 20 cm. Thereafter, it was heated at 140° C. for 30 minutes in a hot air circulation type drying oven to dry and harden it. Furthermore, clear paint "Magiclon 7100" (product name: Kansai Paint Co., Ltd., acrylic/melamine solvent paint) was applied using a small spray gun (W-101, manufactured by Anest Iwata Co., Ltd.) at a booth temperature of 20°C and a humidity of 75°C. % so that the cured coating film had a thickness of 25 to 35 μm. After coating, the coating was allowed to stand at room temperature for 15 minutes, and then heated at 140° C. for 30 minutes in a hot air circulation drying oven to dry and harden to obtain a multilayer coating. The obtained coated plate having a multilayer coating of the metallic base coating layer (I), the retroreflective layer (II), and the clear coating layer (III) was used as a test plate, and various evaluations were performed.

(Note 1) Retroreflective paint composition; Unibeads UB-02M (BaO-SiO ₂ - _TiO2 -based glass beads, average particle size 45 μm, refractive index 1.93, specific gravity 4.2, manufactured by Union Co., Ltd.) 100 parts, diluted with an organic solvent (butyl acetate) until the solid content was 40% by mass, A retroreflective paint composition was obtained.

Example 10
Base paint composition No. 1 prepared as described above was applied onto a coating plate on which a gray (N-5) coating had been previously formed using a doctor blade as an object to be coated. 3 was diluted with an organic solvent to adjust the solid content to 25% by mass, and using a small spray gun (W-101 manufactured by Anest Iwata Co., Ltd.), the booth temperature was 20°C, the humidity was 75%, and the discharge pressure was 2.5 kgf/cm2. The cured coating film was coated to a thickness of 30 μm under conditions of a gun distance of 20 cm. After that, it was left to stand at room temperature for 15 minutes, and then a retroreflective paint composition (Note 1) containing high refractive index beads was applied to these uncured painted surfaces (wet-on-wet) using a small spray gun (Anest Iwata Co., Ltd.). The cured coating film was coated to a film thickness of 15 μm using the company's W-101) under conditions of a booth temperature of 20° C., humidity of 75%, discharge pressure of 2.5 kgf/cm ² , and gun distance of 20 cm. Thereafter, it was heated at 140° C. for 30 minutes in a hot air circulation type drying oven to dry and harden it. Furthermore, clear paint "Magiclon 7100" (product name: Kansai Paint Co., Ltd., acrylic/melamine solvent paint) was applied using a small spray gun (W-101, manufactured by Anest Iwata Co., Ltd.) at a booth temperature of 20°C and a humidity of 75°C. % so that the cured coating film had a thickness of 25 to 35 μm. After coating, the coating was allowed to stand at room temperature for 15 minutes, and then heated at 140° C. for 30 minutes in a hot air circulation drying oven to dry and harden to obtain a multilayer coating. The obtained coated plate having a multilayer coating of the metallic base coating layer (I), the retroreflective layer (II), and the clear coating layer (III) was used as a test plate, and various evaluations were performed.

Example 11
Base paint composition No. 1 prepared as described above was applied onto a coating plate on which a gray (N-5) coating had been previously formed using a doctor blade as an object to be coated. 3 was diluted with an organic solvent to adjust the solid content to 25% by mass, and using a small spray gun (W-101 manufactured by Anest Iwata Co., Ltd.) at a booth temperature of 20 ° C., humidity of 75%, and discharge pressure of 2.5 kgf/cm. ^2. Painting was performed at a gun distance of 20 cm so that the cured coating film had a thickness of 10 μm. Thereafter, it was left at room temperature for 15 minutes, and then heated at 140° C. for 30 minutes in a hot air circulation drying oven to obtain a cured coating film with a thickness of 10 μm. A retroreflective paint composition (Note 1) containing high refractive index beads was sprayed onto the cured coating surface using a small spray gun (W-101 manufactured by Anest Iwata Co., Ltd.) at a booth temperature of 20°C and humidity of 75%. The coating was applied under the conditions of a pressure of 2.5 kgf/cm ² and a gun distance of 20 cm so that the cured coating film had a thickness of 15 μm. Thereafter, it was heated at 140° C. for 30 minutes in a hot air circulation type drying oven to dry and harden it. Furthermore, clear paint "Magiclon 7100" (product name: Kansai Paint Co., Ltd., acrylic/melamine solvent paint) was applied using a small spray gun (W-101, manufactured by Anest Iwata Co., Ltd.) at a booth temperature of 20°C and a humidity of 75°C. % so that the cured coating film had a thickness of 25 to 35 μm. After coating, the coating was allowed to stand at room temperature for 15 minutes, and then heated at 140° C. for 30 minutes in a hot air circulation drying oven to dry and harden to obtain a multilayer coating. The obtained coated plate having a multilayer coating of the metallic base coating layer (I), the retroreflective layer (II), and the clear coating layer (III) was used as a test plate, and various evaluations were performed.

Comparative example 3
Base paint composition No. 1 prepared as described above was applied onto a coating plate on which a gray (N-5) coating had been previously formed using a doctor blade as an object to be coated. 3 was diluted with an organic solvent to adjust the solid content to 25% by mass, and using a small spray gun (W-101 manufactured by Anest Iwata Co., Ltd.) at a booth temperature of 20 ° C., humidity of 75%, and discharge pressure of 2.5 kgf/cm. ^2. Painting was performed at a gun distance of 20 cm so that the cured coating film had a thickness of 10 μm. Thereafter, a retroreflective paint composition was not applied to the metallic base coating film (I) that was allowed to stand for 15 minutes at room temperature, and a clear paint composition "Magicron 7100" (trade name: Kansai Paint Co., Ltd., Acrylic・Cure melamine-based solvent paint using a small spray gun (W-101 manufactured by Anest Iwata Co., Ltd.) at a booth temperature of 20°C and humidity of 75% to a film thickness of 25 to 35 μm. Painted. After painting, it was left at room temperature for 15 minutes, and then heated at 140°C for 30 minutes in a hot air circulation drying oven to dry and harden it to form a multilayer coating film that does not have a retroreflective layer (II). Obtained.

The coated plate having the obtained multilayer coating film was used as a test plate, and various evaluations were performed.

In addition, in each evaluation, A and B are passed, and C is failed. If even one of the samples is rated as failing, the multilayer coating film is rejected.

The various test items are as follows.

Note that a multi-angle spectrophotometer (trade name "MA-68II") was used as a colorimeter.

Test item 1: Finishing (appearance)
Appearance 1: Illuminate the prepared coated plate with an artificial sun lamp (manufactured by SELIC Co., Ltd., color temperature 6500K) and observe it by changing the angle of the test plate relative to the illumination. Visual observation was made for any abnormality in the appearance of the coating film, such as dust or lumpiness, and the finish was evaluated based on the following criteria. Here, shade means observing the multilayer coating at an angle that is not affected by specularly reflected light, and means observing from around 110° when the specularly reflected light shown in Figure 1 is 0°. do. Face means observing the multilayer coating from an angle between the highlight and shade, and means observing from the 45° direction in FIG. 1.

A: In the shade, there is no paint film abnormality such as cloudiness, dust, dirt, etc., and the paint is good. B: In the shade, either cloudiness or dust or dirt is slightly observed. C: In the shade, cloudiness, dust, dirt, etc. are observed. It will be done.

Appearance 2: When the same coated board is viewed from the shade direction shown in Figure 1, visually observe whether there is a yellowish tinge in the reflected light and whether there is any unevenness in the iridescent interference light, and evaluate the finish according to the following criteria. evaluated.
A: The shade has no yellowish or uneven iridescent interference light and is excellent in design.B: The shade has a slight yellowish or uneven iridescent interference light.C: The shade has no yellowish or uneven iridescent interference light. Significantly uneven iridescent interference light was observed, which is not desirable as a design.

Appearance 3: The same coated board was illuminated with an artificial sun lamp (manufactured by SELIC Co., Ltd., color temperature 6500K), and the angle of the test board relative to the illumination was changed to observe the thickness of the metallic from the highlight to the shade as shown in Figure 1. The texture and depth were visually observed, and the finish was evaluated based on the following criteria.

A: Very good, with strong metallic brilliance in a wide range from highlights to shades, and a sense of depth or solidity.
B: A wide range of metallic brilliance is observed from the highlight to the shade, but there is a slight sense of depth or solidity.
C: There is almost no sense of depth or depth from the highlight to the shade.

Test item 2: Retroreflectivity
The degree of retroreflectivity of the obtained coating film was visually observed and evaluated. Light was irradiated with a flashlight from a distance of 3 m perpendicularly to a 10 cm x 15 cm painted test board in a dark room (during the day, with blinds blocking external light and indoor lights turned off). The surface of the coating film at this time was observed with the naked eye at a position having an angle of 5 degrees with the light source (3 m away from the coating test plate), and evaluated according to the following criteria.
A: Retroreflection is recognizable and good.
B: Retroreflection is recognizable but somewhat weak.
C: No retroreflection was observed.

Claims (3)

on the object to be coated,
A base coating composition containing an aluminum pigment (a1) and/or an interference pigment (a2) as a glitter pigment , the total amount of the aluminum pigment (a1) and/or interference pigment (a2) in the base coating composition. A base coating composition having a content in the range of 5 to 20 parts by mass based on 100 parts by mass of resin solids of the base coating composition is applied to form a metallic base coating layer (I) as a reflective layer. Process (1),
Step (2) of forming a retroreflective coating layer (II) by coating a retroreflective coating composition containing high refractive index beads having a refractive index within the range of 1.5 to 2.3 ;
Next, a step (3) of coating at least one layer of a clear coating composition to form a clear coating layer (III);
A method for forming a multilayer coating film comprising in this order, the formation of a multilayer coating film having retroreflectivity, characterized in that the L*45 value of the metallic base coating layer (I) is 50 or less. Method. The base coating composition contains an aluminum pigment (a1) and an interference pigment (a2), and the mass ratio of the aluminum pigment (a1) and the interference pigment (a2) is (a1/a2) = 20/80 to The method for forming a multilayer coating film having retroreflectivity according to claim 1 , wherein the ratio is within the range of 50/50. In step (2), a retroreflective coating composition is sprayed onto the uncured metallic base coating layer (I) obtained in step (1) to form a retroreflective coating layer (II). The method for forming a multilayer coating film having retroreflectivity according to claim 1 or 2 , characterized in that:

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