JP2021013898A - Method for formation of multi-layer coating film with retroreflective ability - Google Patents

Abstract

To provide a method for formation of a multi-layer coating film with retroreflective ability by which a coating film, which has a profound and shining metallic appearance when vied from whole angle, exhibits sufficient retroreflective ability with high brightness during night, and has both of high-class design and functionality.SOLUTION: A method for formation of a multi-layer coating film with retroreflective ability includes: a process (1) in which a base paint composition containing an aluminum pigment (a1) and/or an interference pigment (a2) as a brilliant pigment is coated on a coated object to form a metallic base coating film layer (I) as a reflective layer; a process (2) in which a retroreflective paint composition containing beads with high refractive index is coated to form a retroreflective coating film layer (II); and then a process (3) in which at least one layer of clear paint composition is coated to form a clear coating film layer (III); in this order. In this method, L*45 value of the metallic base coating film layer (I) is 50 or less.SELECTED DRAWING: Figure 1

Description

The present invention relates to a method for forming a multi-layer coating film having both high-grade and profound design and retroreflective properties.

Retroreflection is an optically special reflection mechanism, and refers to a reflection phenomenon in which incident light returns to the incident direction again. Unlike specular reflection, where the angle of incidence and the angle of reflection are equal, the received light is reflected back to the light source as it is, which has the effect of improving visibility from the direction of the light source, so it is used for traffic display and reflection display of vehicles. There is.

In order to obtain a laminated structure that exhibits this retroreflective property, it has been conventionally known to form this retroreflective structure by a painting method. For example, in Patent Document 1, a metallic coating film layer containing a brilliant pigment obtained by crushing a vapor-deposited metal film into metal fragments and glass beads on a road wheel base material whose base coating film layer is formed of a powder coating film. A method for forming a brilliant coating film, which sequentially forms a coating film layer containing the above and a clear coating film layer, is disclosed. The retroreflective structure by painting is relatively inexpensive and can be easily painted on any shape, but in order to obtain sufficient retroreflectiveness, a metallic coating layer with high reflectance and glass beads are densely placed on it. I had to spread it all over. That is, it is common that the retroreflective layer contains glass beads as a retroreflective material at a high concentration, for example, 80% by weight or more. The metallic coating film usually has a large change in brightness depending on the angle (usually, it is preferable that the value of L * ₁₅ / L * ₇₅ having high flip-flop property is high), and the reflective layer is a metallic coating film layer. In some cases, the difference in brightness depending on the angle is large, and the obtained multi-layer coating film has a problem that glare and unevenness are noticeable when viewed at a certain angle, and a high-class design is imparted.

On the other hand, among metallic designs, for example, a paint color such as a gun metallic color (black iron color having a luster like a gun) is one of the popular paint colors that have a profound feeling and are deep-rooted. The gun metallic color has a lower lightness than the general silver metallic color, and it is a paint color whose unevenness is difficult to control.

As a method for forming such a low-brightness silver metallic color coating film, for example, Patent Document 2 uses a base coat using a brilliant paint composition containing an aluminum flake pigment and an interfering mica pigment having a dark region in a specific ratio. A coating film forming method for forming a top coat layer using a clear paint after forming a layer is disclosed. Even when the hue of the coating film is a deep color system, it is possible to obtain a deep color tone without emitting an interference color and causing a feeling of white blur in the shade portion.

However, when a bead layer is further formed as a retroreflective layer on such a base coat layer, due to the unique optical characteristics of the beads, a yellowish or milky white turbidity in the shade region (tanning direction), from all angles. There was a problem that it did not look like a beautiful gun metallic, such as uneven interference color when viewed. In addition, compared to when a normal metallic coating film is formed on the reflective layer, the gun metallic color absorbs a part of the incident light in order to aim for a design with low brightness, and the brightness tends to be low as a whole. It is difficult to obtain retroreflectivity. Further, when a coloring pigment such as carbon black is used to reduce the brightness, the retroreflected light may be yellowish, which causes a problem that a beautiful gunmetal design cannot be obtained.

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

When viewed from all angles, it has a profound and shining metallic appearance, exhibits sufficient retroreflectiveness with high brightness at night, and has a luxurious and profound design and functionality. To provide a method for forming a multi-layer coating film having retroreflective properties, which can be obtained.

As a result of diligent studies to solve the above problems, the present inventors have applied an aluminum pigment and / or an interfering pigment as a brilliant pigment to the reflective layer at a specific ratio in a method for forming a multi-layer coating film having retroreflective properties. By using the contained base paint composition to set the L value to a specific value or less, a shining metallic design with a more profound feeling and a high-class feeling can be obtained, and when viewed from all angles, especially in the shade region, the brightness is high. We have found that a multi-layer coating film having retroreflective properties can be obtained, and arrived at the present invention.

That is, the present invention includes the following aspects.

Item 1. A step (1) of coating a base coating composition containing an aluminum pigment (a1) and / or an interference pigment (a2) as a bright pigment on an object to be coated to form a metallic base coating layer (I) as a reflective layer. ),
A step (2) of coating a retroreflective coating composition containing high refractive index beads to form a retroreflective coating layer (II), and then coating at least one clear coating composition to form a clear coating layer (III). ), Step (3),
In this order, a method for forming a multi-layer coating film, wherein the metallic base coating film layer (I) has an L * 45 value of 50 or less, and the multi-layer coating film has retroreflective properties. Method.

Item 2. The total content of the aluminum pigment (a1) and the interfering pigment (a2) in the base coating composition is in the range of 5 to 20 parts by mass based on 100 parts by mass of the resin solid content of the base coating composition. The method for forming a multi-layer coating film having retroreflectivity according to 1.

Item 3. Item 2. The double-reflective property according to Item 1 or Item 2, wherein the mass ratio of the aluminum pigment (a1) and the interfering pigment (a2) is in the range of (a1 / a2) = 20/80 to 50/50. Method of forming a layer coating film.

Item 4. Any one of Items 1 to 3, wherein in the step (2), the retroreflective coating composition is spray-coated on the uncured base coating to form the retroreflective coating layer (II). The method for forming a multi-layer coating film having retroreflective properties according to the section.

The obtained multi-layer coating film has a brilliant metallic appearance that is less angle-dependent and has a profound feeling when viewed from all directions, and has high photoretroreflective ability even in a gunmetal color with relatively low brightness at night. It is possible to obtain a coating film that has both design and functionality.

Further, since the base coating layer (I) and the retroreflective coating layer (II) are excellent in adhesion, the topcoat coating can be applied without dropping the high refractive index beads, and the topcoat clear coating can be applied. It also has excellent adhesion to the membrane layer (III).

An example of the coating film structure of the present invention, a gloss distribution due to a variable angle, and an image of retroreflected light.

<< Method of forming a multi-layer coating film with retroreflective properties >>
In the method for forming a multi-layer coating film having retroreflective property of the present invention, a base coating composition containing an aluminum pigment (a1) and / or an interference pigment (a2) is coated on an object to be coated to obtain a metallic base coating film. Step (1) of forming the layer (I) as a reflective layer,
A step (2) of coating a retroreflective coating composition containing high refractive index beads to form a retroreflective coating layer (II), and then coating at least one clear coating composition to form a clear coating layer (III). ) Is a method for forming a multi-layer coating film, which comprises the step (3) in this order.
The metallic base coating film 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 is useful for articles such as exteriors and interiors of buildings, structures, vehicles, electric appliances, and the like. For example, car bodies or parts of railroad vehicles, aircraft, ships, automobiles, motorcycles, bicycles, three-wheeled vehicles, one-wheeled vehicles, etc .; road peripheral members such as soundproof walls, tunnel interior boards, guard rails; siding materials, tiles, glass, sashes, net doors, etc. House-related materials such as gates, carports, solariums, veranda materials, roof materials, housing exterior wall materials, bathroom mirrors, bathroom walls, bathtubs, makeup mirrors, sanitary ware; show windows, refrigerated product cases, frozen product cases, etc. Store-related materials; home electric products such as mobile phones, audio equipment, and personal computers.

The material of the base material of these objects to be coated is not particularly limited, and for example, iron, aluminum, brass, copper, stainless steel, tin, zinc-plated steel, and alloyed zinc (Zn-Al, Zn-Ni, Zn). -Fe, etc.) Metal materials such as plated steel; polyethylene resin, polypropylene resin, acrylonitrile-butadiene-styrene (ABS) resin, polyamide resin, acrylic resin, vinylidene chloride resin, polycarbonate resin, polyurethane resin, epoxy resin and other resins and various types Plastic materials such as FRP; inorganic materials such as glass, cement and concrete; wood; fiber materials (paper, cloth, etc.) and the like. Among them, at least one selected from a metal material and a plastic material is preferable. These materials may be in the state of a flat plate or may be processed and molded into a desired shape.

An undercoat, an intermediate coating, a coloring base coating, or the like 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 film layer (I) as a reflective layer>
The method for forming a multi-layer coating film of the present invention is a step of coating a base coating composition containing an aluminum pigment (a1) and / or an interfering pigment (a2) to form a metallic base coating layer (I) as a reflective layer. It is characterized in that the L * 45 value of the metallic base coating film layer (I) including (1) is 50 or less.

The metallic base coating composition is a coating composition containing a bright bright pigment, a vehicle-forming resin composition, and if necessary, an additive for coating, etc., as a material capable of expressing a design having a glaring metallic feeling. It is a thing.

The metallic base coating film as the metallic base coating film layer (I) is coated with the metallic base coating composition and finally heated and dried to form a cured coating film. The cured film thickness of the metallic base coating film is preferably 5 to 40 μm, preferably 8 to 30 μm, and more preferably 10 to 20 μm from the viewpoint of achieving both designability and retroreflective property.

In the present invention, the L * value is measured by irradiating light from an angle of 45 ° with respect to an axis perpendicular to the measurement target surface using a multi-angle spectrophotometer, and the reflected light is perpendicular to the measurement target surface. It is a value when L *, a *, and b * (JIS Z 8729 (2004)) are measured for light in a different direction (light received at an angle of 45 ° with respect to positively 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) and the like can be used. In the present specification, the L * 45 value measured using the MA-68II in the cured coating film 15μ is used as a reference.

Such a metallic base coating layer having an L * 45 value of 50 or less, preferably 1 to 45 can be obtained by adjusting the pigment component of the base coating composition, but in the present application, the design and retroreflection From the viewpoint of compatibility of properties, it is essential to use an aluminum pigment (a1) and / or an interfering pigment (a2) as the bright pigment. From the viewpoint of obtaining a strong and profound metallic feeling, the aluminum pigment (a1) is preferably essential, and from the viewpoint of the design and the brighter retroreflective property, the aluminum pigment (a1) and the light interference pigment (a1) It is preferable to use a2) together.
Aluminum pigment (a1)
The aluminum pigment is a pigment containing aluminum, in order to conceal the underlying layer under the metallic base coating film, to obtain a coating film having a glaring metallic luster, and to obtain sufficient retroreflectivity. Used for.

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

The aluminum flake pigment is a flake-shaped pigment based on aluminum.

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

In particular, it is preferable to use an aluminum pigment having 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 from the viewpoint of the balance between the profound design and the good retroreflective property.

The IV value is an abbreviation for Integrity Value, and is a numerical value indicating the brightness in highlights. The smaller the value, the darker the value, and the higher the value, the brighter the color.

In the present specification, the IV value of a coating film containing an aluminum pigment shall be defined as a numerical value measured using "Alcorp LMR-200H" of a coating film manufactured by Kansai Paint Co., Ltd. and coated under predetermined conditions. To do. Further, in the present specification, the IV value is a special value indicating the brightness of the aluminum pigment.

As the aluminum pigment, either one of the aluminum flake pigment and the 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 pigment is roughly classified into two types, leafing and non-leafing, depending on the orientation behavior in the coating film, and either one may be used or both may be used.

Generally, the smaller the average particle size of the aluminum pigment, the higher the coating film hiding property. The larger the average particle size, the better the sparkle feeling (brightness feeling). Aluminum pigments having an average particle diameter (D50) in the range of 6 to 14 μm have a small particle diameter, a medium particle diameter in the range of 15 to 22 μm, and a large particle diameter in the range of more than 22 μm and 100 μm or less. , These may be used alone or in combination.

Interfering pigment (a2)
When the interfering pigment (a2) is contained, the interfering light and the transmitted light expressed by the interfering pigment (a2) are mixed with the reflected light peculiar to the high refractive index beads to improve the brightness and the base coating film. It is particularly preferable because it has the effects of adjusting the tint and improving the retroreflective property without impairing the profound design of the light.

Interference color is caused by the phenomenon that when light is reflected by a substance, the reflected light has a phase difference, and a specific wavelength is strengthened or weakened. Pigments with such an action are called interference pigments. It may be called a pearl luster pigment or a pearl pigment, but it includes these.

Specifically, for example, natural mica, artificial mica, glass, iron oxide, aluminum oxide (excluding those classified as the above aluminum pigment (a1) or the extender pigment described later), various metal oxides such as titanium oxide, etc. Examples thereof include transparent to translucent flaky photo-interfering pigments. These may be used alone or in combination of two or more.

Natural mica is a scaly base material obtained by crushing ore mica (mica).

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 fluorosilicate mineral obtained by mixing an industrial raw material such as ₆ at a constant ratio, heating it, melting it at a high temperature of about 1500 ° C., crystallizing it, cooling it, and then mechanically pulverizing it. For example, as such
KMg ₃ (AlSi ₃ O ₁₀ ) F ₂ : Potassium Fluorine Phlogopite,
KMg 2.1 _{/ 2} (Si ₄ O ₁₀ ) F ₂ : Potassium tetrasilicon mica,
KMg ₂ Li (Si ₄ O ₁₀ ) F ₂ : Potassium teniolite,
Namg ₃ (AlSi ₃ O ₁₀ ) F ₂ : Sodium phlogopite,
Namg ₂ Li (Si ₄ O ₁₀ ) F ₂ : Sodium teniolite,
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,
And so on. Compared to natural mica, artificial mica has less impurities and is uniform in size and thickness.

Metal oxide-coated mica and / or metal oxide-coated glass flakes are preferable, and titanium oxide-coated synthetic mica is particularly preferable, from the viewpoint of obtaining transparent and highly bright retroreflected light. The coated mica of the metal oxide-coated mica may be either natural or synthetic.

A pigment having a layered structure of at least one layer or more, in which mica, glass flakes, or the like is coated with a metal oxide such as titanium oxide to form a layer. Examples of commercially available products include metal oxide-coated mica such as titanium oxide-coated interfering mica pigment, metal oxide-coated alumina flakes, and metal oxide-coated glass flakes. As the interference pigment, those commercially available from each company 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 for further improving dispersibility, water resistance, chemical resistance, weather resistance and the like.

Examples of the type of interference color of the interference pigment (a2) include silver, gold, red, purple, blue, and green, and the color of the 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 reducing the deeper metallic feeling and the yellowness of the highlight during retroreflection. In the present invention, the "interference color" refers to the color tone of the reflected interference light of the structural color developed by the interference pigment.

Of these, the content of the interfering pigment having a blue interfering color is 1 to 10% by mass with respect to 100 parts by mass of the resin solid content of the base coating composition from the viewpoint of retroreflectivity and designability. It is preferably contained in the range of 2 to 8 parts by mass.

The resin solid content of the base coating composition is the non-volatile content of the coating film-forming resin (vehicle-forming resin) described later.

The base coating composition contains other pigments (a3) other than the aluminum pigment (a1) and the interfering pigment (a2) as pigment components within a range that does not impair the design and retroreflectivity of the present invention. You may.

Other pigments (a3)
Examples of other pigment components include extender pigments, coloring pigments, and bright pigments other than the aluminum pigment (a1) and the interference pigment (a2).

Examples of the extender pigment include clay, kaolin, barium sulfate, barium carbonate, calcium carbonate, talc, silica, alumina white and the like, and among them, 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, isoindolin pigments, slene pigments, and perylene pigments. Examples thereof include dioxazine pigments and diketopyrrolopyrrole pigments, and among them, titanium oxide and carbon black can be preferably used. In particular, as a coloring pigment, at least one coloring pigment having a complementary color relationship with a black pigment (for example, carbon black) is used in order to achieve both a profound design with low lightness and an improvement in retroreflectivity while suppressing yellowness. It is preferable to use seeds [red (eg, quinacridone red) and blue (eg, phthalocyanine blue)] in combination.

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

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

Content and content ratio The total content of the pigment in the base coating composition is such that the L * 45 value of the obtained coating film is 50 or less from the viewpoint of a profound design. It can be appropriately adjusted within the range of 1 to 30 parts by mass with reference to 100 parts by mass of the resin solid content of.

In particular, the aluminum pigment (a1) in the base coating composition is from the viewpoint of exhibiting the design of the obtained multi-layer coating film and the retroreflectivity having high brightness when viewed from all angles, especially in the shade region. The total content of the interfering pigment (a2) is preferably in the range of 5 to 20 parts by mass, and further in the range of 8 to 18 parts by mass, based on 100 parts by mass of the resin solid content of the base coating composition.

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

When the aluminum pigment (a1) is contained, the content thereof is 0.5 to 10 parts by mass, preferably 1 to 9 parts by mass, based on 100 parts by mass of the resin solid content of the base coating composition. Within the range is preferred.

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

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

The vehicle-forming resin used in the base coating composition may contain a resin generally used as a coating resin (sometimes referred to as a vehicle-forming resin) and a curing agent, for example, a coating resin. Examples thereof include coating film-forming resins such as acrylic resin, polyamide resin, urethane resin, polyester resin, and epoxy resin. As the coating film-forming resin, it is preferable to use a curing agent and a resin capable of cross-linking with the curing agent, 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, a hydroxyl group-containing acrylic resin and / or a hydroxyl group-containing polyester resin is preferable. Examples of the curing agent include amino resins such as melamine resin, guanamine resin and urea resin, polyisocyanate compounds typified by isophorone diisocyanate (IPDI), hexamethylene diisocyanate (HMDI) and the like, or dimer or trimeric thereof; polyisocyanate. Examples thereof include a prepolymer obtained by subjecting a compound to a polyhydric alcohol, a low molecular weight polyester resin, water, or the like in a urethanization reaction under conditions where an isocyanate group is excessive. Further, a polyisocyanate compound in which the isocyanate group is blocked with a blocking agent can also be used. Examples of the blocking agent include phenols; oximes; lactams; alcohols; mercaptans; active methylene compounds such as diethyl malonate. When a blocked polyisocyanate compound is used, it is preferable to use a dissociation catalyst of a blocking agent in combination. These can be used alone or in combination of two or more.

The base coating composition may further contain a rheology control agent such as polymer fine particles, a plasticizer, a diluent such as an organic solvent, and the like as an additive as long as the transparency and design are not impaired. When these additives are contained, it is preferably 20 parts by mass or less, preferably 0.01 to 15 parts by mass, based on 100 parts by mass of the resin solid content in the base coating composition. ..

As a coating method of the base coating composition, for example, it can be coated by spray coating such as an air spray, an airless spray, and a rotary atomization coating machine, and electrostatic application may be performed at the time of coating.

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

The form of the base coating composition may be an organic solvent type coating composition, a water-based or water-soluble coating composition, a solvent-free coating composition or a powder coating composition which does not substantially contain a solvent or the like, but the design may be used. From the viewpoint of properties, an organic solvent type coating composition is preferable. In the present specification, the organic solvent type coating composition is a coating material that does not substantially contain water as a solvent.

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

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

The cured state of the base coating film (I) may be either cured or uncured, but the retroreflective coating composition is sprayed onto the uncured base coating film from the viewpoint of designability and retroreflectivity. It is preferable to paint to form the retroreflective coating layer (II).

Painting on the uncured coating film may be referred to as wet-on-wet. Wet-on-wet refers to coating in a state where the coating film is not substantially cured, a state in which the coating film is not substantially cured is an uncured coating film, and an uncured coating film is a coating film. It is a state that has not reached the following cured and dried state, and includes a touch-dried state and a semi-cured and dried state specified in JIS K 5600-1-1. The cured coating film is a cured and dried state specified in JIS K 5600-1-1 (2004), that is, the center of the coated surface is strongly sandwiched between the thumb and the index finger, and the coated surface is not dented by fingerprints. The coating film is in a state where the movement of the coating film is not felt, and the center of the coated surface is rapidly and repeatedly rubbed with the fingertip to leave no scratches on the coated surface.

When the retroreflective coating composition of the present invention is applied in a state where the base coating is uncured, high refractive index beads are easily embedded in the base coating layer due to the spray pressure during spray coating, and at the same time, the uncured base coating is applied. Since the bright pigment inside is likely to be oriented so as to surround the high refractive index beads, it is particularly preferable because it has an effect of exhibiting sufficient retroreflection.

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

The average particle size (D50) of the high refractive index beads is preferably in the range of about 5 to 100 μm, more preferably in the range of 10 to 60 μm, and particularly preferably in the range of 30 to 50 μm. Further, in order to better generate the interference action in the reflected light, the particle size distribution of the high refractive index beads is preferably as narrow and sharp as possible, and the particle size distribution contains 80% by weight or more of the particle size of 25 to 60 μm. Those are particularly preferably used.

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

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

As a method of coating the retroreflective coating composition, for example, it can be coated by spray coating such as an air spray, an airless spray, and a rotary atomization coating machine, and electrostatic application may be performed at the time of coating.

The coating film thickness of the retroreflective coating film is usually in 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 coating film layer and designability. can do.

The retroreflective coating film layer (II) itself can be heat-cured at a temperature of about 100 to 180 ° C., but the retroreflective coating film layer is formed on the uncured base coating film layer and is heat-cured at the same time. Since the high-reflectivity beads can be arranged in a single layer state and can be arranged very close to the bright pigment in the base layer, the recursion is efficiently performed while showing an excellent design with a glaring and profound feeling and a high-class feeling. Reflexivity can be expressed.

As preheating, preheating, air blow, or the like may be performed. The preheat temperature is about 40 to 100 ° C., preferably about 50 to 90 ° C., and 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 air blow can be usually performed by blowing air heated to room temperature or a temperature of about 25 ° C. to 80 ° C. for about 30 seconds to 15 minutes on the coated surface of the object to be coated.

The temperature of the baking treatment is usually in the range of 100 to 180 ° C., particularly preferably 110 to 160 ° C. The baking treatment time is usually preferably 10 to 60 minutes.

The form of the retroreflective coating composition may be an organic solvent type, a water-based or water-soluble coating material, a solvent-free or powder that does not substantially contain a solvent, etc., but in terms of designability and good retroreflective expression. Therefore, it is preferable that the composition is an organic solvent type coating composition.

The retroreflective coating composition used in the present invention uses a diluent as necessary at the time of coating, and has a solid content of 15% by mass or more, particularly preferably in the range of 35 to 60% by mass, and a viscosity of 5 to 5. It is preferable to adjust the temperature within the range of 30 seconds / Ford cup # 4/20 ° C. from the viewpoint of designability, coating workability, and reduction of the amount of organic solvent discharged.

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

As the clear coating composition of the present invention, conventionally known clear coating compositions can be used without limitation. For example, a liquid or powder coating composition containing a substrate resin and a cross-linking agent can be applied. Examples of the base resin include acrylic resins, polyester resins, alkyd resins, fluororesins, urethane resins, silicon-containing resins and the like, which contain crosslinkable functional groups such as hydroxyl groups, carboxyl groups, silanol groups and epoxy groups. The cross-linking agent contains a melamine resin, a urea resin, a polyisocyanate compound, a blocked polyisocyanate compound, an epoxy compound or a resin, a carboxyl group-containing compound or a resin, an acid anhydride, and an alkoxysilane group that can react with the functional group of the substrate resin. Examples include compounds and resins. These may be used alone or in combination of two or more.

Further, if necessary, a solvent such as water or an organic solvent, an additive such as a curing catalyst, a defoaming agent, and an ultraviolet absorber can be appropriately added. The form of the clear coating composition may be an organic solvent type, a water-based or water-soluble coating material, a solvent-free or powder containing substantially no solvent, etc. The clear coating composition in the present invention impairs transparency. Coloring pigments may be appropriately contained within the range. As the coloring pigment, one kind or a combination of two or more kinds of pigments conventionally known for inks and paints may be contained. The amount to be added may be appropriately determined, but is 30 parts by weight or less, preferably 0.1 to 10 parts by weight, based on 100 parts by mass of the film-forming resin composition in the clear coating composition.

As a coating method of the clear coating composition, for example, it can be coated by spray coating such as an air spray, an airless spray, and a rotary atomizing coating machine, and electrostatic application may be performed at the time of coating.

The coating film thickness of the clear coating film is preferably such that it covers the high-refractive-index beads from the viewpoint of preventing the high-refractive beads from falling off, uniform design, and evenly expressing retroreflectivity. It can be usually in the range of 5 to 60 μm, preferably in the range of 10 to 45 μm.

In the present invention, when the clear coating composition is coated without heat-curing the coating film of the base coating composition and / or the retroreflective coating composition, these coating films are coated after the clear coating composition is applied. May be heat-cured at the same time. The coating film itself of the clear coating composition can be cured at a temperature of about 70 to about 150 ° C.

By this method, the base coating composition functions as a reflective layer, and when a high refractive index bead layer is formed, it has a retroreflective property that achieves both a profound feeling and a high-class design and a high-brightness retroreflective property. A multi-layer coating can be formed.

The multi-layer coating film having retroreflective properties obtained by the method of the present invention has a profound feeling from any angle such as highlights and shades even when the L * 45 value of the base coating film is as low as 50 or less. It has a certain brilliant metallic appearance, exhibits sufficient retroreflectiveness at high brightness at night, and can obtain a coating film having a high-class design and functionality.

Hereinafter, the present invention will be described in more detail with reference to examples. In addition, "part" and "%" indicate "mass part" and "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) is measured by a gel permeation chromatograph (gel permeation chromatograph: GPC) using a standard polystyrene calibration curve. "HLC-8120GPC" (trade name, manufactured by Tosoh Corporation) is used as the gel permeation chromatograph, and one "TSKgel G4000HXL", two "TSKgel G3000HXL", and one "TSKgel G2000HXL" are used as columns. A total of 4 books (trade names, all manufactured by Tosoh Corporation) are used, a differential refractometer is used as a detector, mobile phase: tetrahydrofuran, measurement temperature: 40 ° C., flow velocity: 1 mL / min. Can be measured with.

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

(3) Preparation of light brightness paint / coating film Acrylic No. 5 g of aluminum pigment. Add 8 g of 2000GL thinner (manufactured by Kansai Paint Co., Ltd.), pre-disperse, and further, click No. 97g of 2026GL clear (manufactured by Kansai Paint Co., Ltd.) was added, and the mixture was shaken with a paint shaker for 10 minutes. The obtained silver metallic paint was applied to art paper to form a coating film using a 9 mil applicator, and then dried at room temperature.

Next, research on paints, No. Evaluation was performed using a laser type metallic feeling measuring device Alcorp LMR-200 (manufactured by Kansai Paint Co., Ltd.) according to the method described in 117, pp. 67-72 (published by Kansai Paint Co., Ltd. in 1989). The measurement was performed under optical conditions in which a laser light source was arranged at an incident angle of 45 degrees and a receiver was arranged at a light receiving angle of 0 degrees and −35 degrees. The IV value was determined at a light receiving angle of −35 degrees to obtain the maximum light intensity, excluding the light in the specular reflection region reflected on the surface of the coating film from the reflected light of the laser. The IV value is a parameter proportional to the intensity of specularly reflected light from the aluminum pigment, and represents the magnitude of the light brightness.

Manufacturing example 1
Aluminum pigment (a1) No. 1 per 100 parts by mass (solid content) of a vehicle-forming resin composition consisting of 75 parts of a hydroxyl group-containing acrylic resin (hydroxyl value 100 mgKOH / g, number average molecular weight 20000) and 25 parts of melamine resin. 1 was mixed so as to form 4 parts, and the mixture was stirred and mixed to obtain an organic solvent type metallic base coating composition No. 1 was adjusted.

Production Examples 2-11
In Production Example 1, the organic solvent type base coating composition No. 1 is the same as in Production Example 1 except that the pigment components are as shown in Table 1. 2 to 11 were adjusted.

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

Examples 1-9 and Comparative Examples 1-2
Each base coating composition No. 2 produced as described above was prepared on a coating plate on which a gray (N-5) coating film was 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. Under} the condition that the gun distance was 20 cm, the cured coating film was coated so as to have a film thickness of 10 μm. Then, it was left at room temperature for 15 minutes, and then a retroreflective coating composition (Note 1) containing high refractive index beads was applied to these uncured coated surfaces (wet on wet) with a small spray gun (Anest Iwata Co., Ltd.). Using W-101) manufactured by the company, the cured coating film was coated with a film thickness of 15 μm under the conditions of a booth temperature of 20 ° C., a humidity of 75%, a discharge pressure of 2.5 kgf / cm ² , and a gun distance of 20 cm. Then, it was dried and cured by heating at 140 ° C. for 30 minutes using a hot air circulation type drying oven. Furthermore, the clear paint "Magiclon 7100" (trade name: Kansai Paint Co., Ltd., acrylic / melamine solvent paint) was used with a small spray gun (W-101 manufactured by Anest Iwata Co., Ltd.) at a booth temperature of 20 ° C and humidity of 75. The cured coating film was coated with a film thickness of 25 to 35 μm under the condition of%. After coating, the mixture was left at room temperature for 15 minutes, then heated at 140 ° C. for 30 minutes using a hot air circulation type drying furnace, and dried and cured to obtain a multi-layer coating film. Various evaluations were carried out using the obtained coated plate having the multi-layer coating film of the metallic base coating film layer (I), the retroreflective layer (II) and the clear coating film layer (III) as a test plate.

(Note 1) Retroreflective paint composition; Magiclon 1026 Clear (manufactured by Kansai Paint Co., Ltd., trade name, acrylic / melamine curable resin paint) Unibeads UB-02M (BaO-SiO ₂ −) for 100 parts of resin solid content. TiO _2- 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 becomes 40% by mass. A retroreflective coating composition was obtained.

Example 10
The base coating composition No. 1 prepared as described above was prepared on a coating plate on which a gray (N-5) coating film was 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. Under the condition that the gun distance was 20 cm, the cured coating film was coated so as to have a film thickness of 30 μm. Then, it was left at room temperature for 15 minutes, and then a retroreflective coating composition (Note 1) containing high refractive index beads was applied to these uncured coated surfaces (wet on wet) with a small spray gun (Anest Iwata Co., Ltd.). Using W-101) manufactured by the company, the cured coating film was coated with a film thickness of 15 μm under the conditions of a booth temperature of 20 ° C., a humidity of 75%, a discharge pressure of 2.5 kgf / cm ² , and a gun distance of 20 cm. Then, it was dried and cured by heating at 140 ° C. for 30 minutes using a hot air circulation type drying oven. Furthermore, the clear paint "Magiclon 7100" (trade name: Kansai Paint Co., Ltd., acrylic / melamine solvent paint) was used with a small spray gun (W-101 manufactured by Anest Iwata Co., Ltd.) at a booth temperature of 20 ° C and humidity of 75. The cured coating film was coated with a film thickness of 25 to 35 μm under the condition of%. After coating, the mixture was left at room temperature for 15 minutes, then heated at 140 ° C. for 30 minutes using a hot air circulation type drying furnace, and dried and cured to obtain a multi-layer coating film. Various evaluations were carried out using the obtained coated plate having the multi-layer coating film of the metallic base coating film layer (I), the retroreflective layer (II) and the clear coating film layer (III) as a test plate.

Example 11
The base coating composition No. 1 prepared as described above was prepared on a coating plate on which a gray (N-5) coating film was 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 / cm. ^{2. Under} the condition that the gun distance was 20 cm, the cured coating film was coated so as to have a film thickness of 10 μm. Then, it was left at room temperature for 15 minutes, and then heated at 140 ° C. for 30 minutes using a hot air circulation type drying oven to obtain a cured coating film having a film thickness of 10 μm. A retroreflective coating composition (Note 1) containing high refractive index beads is discharged 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 a humidity of 75%. Under the conditions of a pressure of 2.5 kgf / cm ² and a gun distance of 20 cm, the cured coating film was coated so as to have a film thickness of 15 μm. Then, it was dried and cured by heating at 140 ° C. for 30 minutes using a hot air circulation type drying oven. Furthermore, the clear paint "Magiclon 7100" (trade name: Kansai Paint Co., Ltd., acrylic / melamine solvent paint) was used with a small spray gun (W-101 manufactured by Anest Iwata Co., Ltd.) at a booth temperature of 20 ° C and humidity of 75. The cured coating film was coated with a film thickness of 25 to 35 μm under the condition of%. After coating, the mixture was left at room temperature for 15 minutes, then heated at 140 ° C. for 30 minutes using a hot air circulation type drying furnace, and dried and cured to obtain a multi-layer coating film. Various evaluations were carried out using the obtained coated plate having the multi-layer coating film of the metallic base coating film layer (I), the retroreflective layer (II) and the clear coating film layer (III) as a test plate.

Comparative Example 3
The base coating composition No. 2 produced as described above was prepared on a coating plate on which a gray (N-5) coating film was 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 / cm. ^{2. Under} the condition that the gun distance was 20 cm, the cured coating film was coated so as to have a film thickness of 10 μm. After that, the clear paint composition "Magiclon 7100" (trade name: Kansai Paint Co., Ltd., acrylic) was not applied on the metallic base coating film (I) that had been left at room temperature for 15 minutes. -Melamine-based solvent paint) was used as a cured coating film 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% so that the film thickness was 25 to 35 μm. I painted it. After painting, it is left at room temperature for 15 minutes, and then heated at 140 ° C. for 30 minutes using a hot air circulation type drying furnace to dry and cure to obtain a multi-layer coating film having no retroreflective layer (II). Obtained.

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

In each evaluation, A and B are acceptable, and C is unacceptable. If even one is evaluated as unacceptable, the multi-layer coating film is unacceptable.

Various test items are as follows.

A multi-angle spectrophotometer (trade name "MA-68II") was used as the colorimeter.

Test item 1: Finish (appearance)
Appearance 1: The prepared coated plate is illuminated with an artificial sun lamp (Ceric, color temperature 6500K), and the test plate is observed at different angles with respect to the illumination. Whether or not there is white turbidity when viewed from the shade direction. The finish was evaluated according to the following criteria by visually observing whether there was any abnormality in the appearance of the coating film such as dust and bumps. Here, the shade means observing the multi-layer coating film at an angle that is not affected by the specularly reflected light, and means observing from around 110 ° when the specularly reflected light shown in FIG. 1 is 0 °. To do. The face means observing the multi-layer coating film from an angle between the highlight and the shade, and means observing from the 45 ° direction in FIG.

A: Shade is good with no abnormalities in the coating film such as turbidity and dust and lumps B: Shade is slightly cloudy or dust and lumps are slightly observed C: Shade is cloudy and dust and lumps are recognized Be done.

Appearance 2: When the coated plate is viewed from the shade direction shown in FIG. 1, the presence or absence of yellowness of the reflected light and the unevenness of the iridescent interference light are visually observed, and the finishability is determined according to the following criteria. evaluated.
A: Shade has excellent design without yellowish or uneven iridescent interference light B: Shade with some yellowish or uneven iridescent interfering light C: Shade with yellowish or yellowish Remarkably uneven iridescent interfering light is observed, which is not preferable as a design.

Appearance 3: The coated plate is illuminated with an artificial sun lamp (Ceric, color temperature 6500K), and the test plate is observed at different angles with respect to the illumination. The metallic weight from the highlight to the shade shown in FIG. 1 is heavy. The feeling and depth were visually observed, and the finish was evaluated according to the following criteria.

A: A wide range of metallic brilliance is strongly recognized from highlights to shades, and there is a sense of depth or profoundness, which is very good.
B: A wide range of metallic brilliance is recognized from highlights to shades, but it is slightly deep or profound.
C: From the highlight to the shade, there is almost no sense of depth or profoundness.

Test item 2: Retroreflective
The degree of retroreflectiveness of the obtained coating film was visually observed and evaluated. In a dark room (in the daytime, a blind or the like blocks the light from the outside and the lights in the room are turned off), the light was irradiated by a flashlight from a distance of 3 m perpendicular to the 10 cm × 15 cm coating test plate. The surface of the coating film at this time was visually observed at a position at 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: Retroreflective can be recognized and is good,
B: Retroreflective is recognizable but slightly weak,
C: No retroreflection is observed.

Claims (4)

On the object to be coated
A step (1) of coating a base coating composition containing an aluminum pigment (a1) and / or an interference pigment (a2) as a bright pigment 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).
Next, a step (3) of coating at least one layer of the clear coating composition to form a clear coating film layer (III).
In this order, a method for forming a multi-layer coating film, wherein the metallic base coating film layer (I) has an L * 45 value of 50 or less, and the multi-layer coating film has retroreflective properties. Method. The total content of the aluminum pigment (a1) and / or the interfering pigment (a2) in the base coating composition is within the range of 5 to 20 parts by mass based on 100 parts by mass of the resin solid content of the base coating composition. The method for forming a multi-layer coating film having retroreflectivity according to claim 1. The retroreflectivity according to claim 1 or 2, wherein the mass ratio of the aluminum pigment (a1) and the interfering pigment (a2) is in the range of (a1 / a2) = 20/80 to 50/50. A method for forming a multi-layer coating film. Any of claims 1 to 3, wherein in the step (2), the retroreflective coating composition is spray-coated on the uncured base coating to form the retroreflective coating layer (II). The method for forming a multi-layer coating film having retroreflective properties according to item 1.

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