Patent Application
20130048501
The present invention relates to a laminated coating film structure formed on a vehicle outer panel and the like.
In the case of coating metal parts such as vehicle outer panels that require weather resistance, a laminated coating film structure is typically employed in which, after forming a lower layer coating film (undercoating film) by electrodeposition coating for the purpose of preventing rust, an intermediate coating film having substrate hiding ability is formed thereon followed by laminating an upper layer coating film (top coating film) thereon. Although the intermediate coating film is provided to enhance light resistance, chipping resistance and coloring, from the viewpoints of conservation of resources, reduction of production steps, reduction of costs and the like, attempts have been made to directly laminate the upper layer coating film on the lower layer coating film without providing the intermediate coating film.
For example, Patent Document 1 (International Publication WO 96/33814) describes the coating of a first color base coat having substrate hiding ability onto a cationic electrodeposited coating film, coating a second color base coat having transparency on the coated film thereof without substantially curing, and heat-curing both color base coats followed by coating with a clear coating. It is described that this is carried out for the purpose of imparting a function of an intermediate coating film to the first color base coat, and that the pigment content is increased so that the light transmission rate of the coating film within a wavelength range of 400 to 700 nm is 5% or less. In addition, it is also described that the pigment content of the second color base coat is lower than the pigment content of the first color base coat. This is carried out to enable the color of the first color base coat to be able to be recognized through the coating film of the second color base coat due to the transparency thereof.
In the case of obtaining vivid coloring with a laminated coating film structure, an intermediate coating film d having good light reflection using a white pigment has conventionally been provided as shown in
Thus, it is necessary to impart substrate hiding ability to the first base coating film a as described in the above-mentioned Patent Document 1 in order to obtain vivid coloring without providing an intermediate coating film. As means for accomplishing this, the addition of an iridescent material (metallic pigment) such as aluminum flakes to the first base coating film a has been considered. However, when an iridescent material is incorporated in the first layer coating film a, hiding of the first layer coating material becomes inadequate at a typical thickness of about 10 um even if the pigment concentration in the second layer coating film b is increased to the maximum coatable concentration. Accordingly, it is difficult to obtain vivid coloring by incorporating an iridescent material in the first base coating film a. Note “um” stands for micro-meter unless otherwise specifically indicated.
In addition, there are additional problems required to be solved in order to obtain vivid coloring. This is readily understood by considering the mechanism by which pigment renders color. For example, in the case or red color, color is rendered as a result of light contacting the pigment, light or short and medium wavelengths being selectively reflected while light of long wavelengths is transmitted, after which the transmitted light is reflected at the surface of other pigment. This selective absorption of light by pigment does not allow the obtaining of adequate selective absorption effects in the case of selective absorption by a single pigment. Adequate selective absorption is only obtained by light passing through the pigment numerous times. A vivid red color can be obtained as a result of this selective absorption. If the pigment content of the coating film is excessively low, light of short and medium wavelengths is not adequately absorbed. As a result, instead of light of long wavelengths only, light of short and medium wavelengths is also reflected. A vivid red color is no longer obtained as a result of this light of short and medium wavelengths being reflected together with light of long wavelengths.
In contrast, enhancing the pigment concentration of a coating film is effective to a certain degree for improving substrate hiding ability and selective absorption and reflection of light. However, there are limitations on the extent to which vivid coloring can be obtained by enhancing the pigment concentration of a coating film. This is due to the reasons indicated below. Since the strength of a coating film is obtained by hardening a pigment with a resin, increasing the pigment concentration results in a corresponding decrease in the amount of resin. Consequently, if vivid coloring is attempted to be obtained by enhancing the pigment concentration of a coating film, it becomes difficult to ensure required coating film strength. Moreover, since coating film viscosity increases as the concentration of pigment increases, spray coating also becomes difficult. In addition, the use of dyes, which are coloring materials that dissolve in coating materials, has been considered instead of pigment. However, although dyes have satisfactory selective absorption properties, they have the problem of being susceptible to fading caused by ultraviolet light.
An object of the present invention is to obtain a laminated coating film structure that enables coloring of a specific color with two coating films consisting a first layer on the side close to a coated object and a second layer on the side far from the coated object, which allows the obtaining of satisfactory coloring without particularly increasing the thickness of the coating film.
One aspect of the present invention is a laminated coating film structure having a laminated coating film that renders a specific color on a coated object, wherein the laminated coating film is provided with a first layer arranged on the side near to the coated object and contains a pigment in which the mean particle diameter thereof is ½ or more the wavelength of the specific color but 2 um or less, and a second layer arranged on the side far from the coated object and contains a pigment in which the mean particle diameter thereof is 0.05 um or more but less than ½ the wavelength of the specific color.
Objects, characteristics, aspects and advantages of the present invention will be made clear by the following detailed description and appended drawings.
With the foregoing in view, the inventors of the present invention conducted various studies while focusing on differences in light absorption and reflection within the same pigment attributable to particle diameter.
The inventors of the present invention surmised that differences in light absorption and reflection of a pigment attributable to particle diameter are the result of the factors described below. As was previously mentioned, the reason why a pigment renders a specific color is that the reflection rate of light of that pigment differs according to wavelength, with the pigment reflecting light of a wavelength of that specific color and absorbing light of other wavelengths. Thus, in the case of red color, for example, when light of short and medium wavelengths is efficiently absorbed by the pigment and light of longer wavelengths is efficiently reflected, vivid red color is rendered.
Here, the wavelength of a specific color refers to the wavelength at which spectral reflectance reaches a peak. Namely, this refers to a wavelength at which light that is radiated onto an object of a specific color and reflected becomes spectral light, and the spectral reflectance that is the reflection rate at each wavelength demonstrates a maximum value. In the case a specific color consists of a mixture of red, orange and yellow, within the visible wavelength range of 380 to 780 nm, the wavelength in the vicinity of a median value of a range in which wavelength increases from the wavelength at which spectral reflectance begins to increase accompanying an increase in wavelength to a maximum wavelength of 780 nm is the peak wavelength at which spectral reflectance demonstrates a maximum value. This wavelength is the specific color wavelength.
Since light is a type of electromagnetic wave and propagates by wave motion, when light a specific color wavelength propagates through a coating film, in plain terms, if light contacts the pigment while passing between the pigment particles, the light is reflected and selectively absorbed as it is transmitted through the particles. Light that passes between the particles is transmitted more easily the smaller the particle diameter of the pigment. In addition, light that passes through the pigment is also transmitted more easily the smaller the particle diameter of the pigment. As light of a specific color is transmitted through the pigment while passing between the pigment particles, since unnecessary wavelengths of light other than that of the specific color have a lower reflection rate than light of the wavelength of the specific color, that light is absorbed by the pigment. As a result, the specific color light has high chroma.
On the other hand, if particle diameter increases even for the same pigment, it becomes more difficult for light of a specific color wavelength to pass between the pigment particles. Namely, the light contacts the pigment particles and is separated into light that is reflected at the particle surface and light that enters the pigment. Light that contacts the pigment surface is reflected more easily. In addition, light that enters the pigment is unable to pass through the pigment particles, and is selectively absorbed in the vicinity of the particle surface layer. Accordingly, a specific color is rendered that does not have high chroma.
According to findings obtained through experiments and the like by the inventors of the present invention, if the particle diameter of a pigment is increased, when the particle diameter thereof has reached the vicinity of ½ of the wavelength of a specific color, the reflection rate of light of the specific color at the surface of the pigment particles reaches a maximum. Although the reflection rate decreases slightly as particle diameter of the pigment subsequently increases, the decrease is not large and a comparatively high reflection rate is obtained. This is thought to be the result of it becoming more difficult for light oscillating at a wavelength of the specific color to pass between the particle pigments as a result of being obstructed by the pigment when the pigment particle diameter increases, thereby making it easier for the light to be reflected at the pigment surface.
As is clear from the above explanation, the following is required for a coating film to vividly render a specific color. It is necessary for light of a specific color to not be reflected at locations close to the paint coating surface, and be transmitted to a certain degree through the coating film by passing between pigment particles. Moreover, when light of a color other than the specific color contacts the pigment particles, that light is required to be transmitted while being selectively absorbed, after which light of the specific color is required to be efficiently reflected without being absorbed.
The following provides an explanation of embodiments of the present invention based on the drawings. The following description of the preferred embodiments is essentially intended to be merely exemplary, and is not intended to limit the present invention, its application targets or its uses.
The laminated coating film structure according to the present embodiment has a laminated coating film that renders a specific color on a coated object, and the laminated coating film is provided with a first layer arranged on a side near the coated object and containing a pigment in which the mean particle diameter thereof is ½ or more the wavelength of the specific color but 2 um or less, and a second layer arranged on a side far from the coated object and containing a pigment in which the mean particle diameter is 0.05 um or more but less than ½ the wavelength of the specific color. Namely, in the laminated coating film structure disclosed herein, in that which attempts to render a specific color with both coating films consisting of a lower first layer and an upper second layer coated onto a coated object, the pigment for rendering the specific color of the first layer has a mean particle diameter that is ½ or more the wavelength of the specific color but 2 um or less, while the pigment for rendering the specific color of the second layer has a mean particle diameter of 0.05 um or more but less than ½ the wavelength of the specific color. Note “um” stands for micro-meter unless otherwise specifically indicated.
As a result, in a coating film of the upper second layer having a small pigment particle diameter, light of a wavelength other than that of the specific color is selectively absorbed while light of the wavelength of the specific color is easily transmitted. Since light of unwanted color wavelengths is absorbed in the coating film of the second layer, a specific color of high chroma can be obtained. In the coating film of the lower first layer, since pigment particle diameter is large and the reflectivity of light of a wavelength of the specific color is good, the lightness of the resulting specific color increases. Naturally, in the coating film of the first layer as well, light of unwanted color wavelengths is absorbed, and as a result thereof, chroma of the reflected specific color increases. As a result, according to the laminated coating film structure described above, a vivid specific color can be rendered without increasing coating film thickness.
Furthermore, the laminated coating film structure according to the present invention uses the wavelength of a specific color rendered by the ultimately obtained laminated coating film structure, namely the wavelength of the target exterior color as a reference for the mean particle diameter of the pigment respectively contained in the first layer and the second layer. In addition, in a structure that uses wavelength of the exterior color as a reference, the specific color exhibits a spectral reflectance distribution for each wavelength in the case of being based on wavelength. The mean particle diameter of the pigment respectively used for the first layer and the second layer is adjusted corresponding to the exterior color of the laminated coating film structure.
In addition, although pigment becomes less advantageous in terms of weather resistance as the particle diameter thereof becomes smaller (and is particularly susceptible to degradation by ultraviolet light), as a result of making the mean particle diameter of the pigment of the second layer 0.05 um or more, it does not impair the ensuring of adequate weather resistance. In addition, although smoothness of the coating film decreases as particle diameter of the pigment increases, as a result of making the mean particle diameter of the pigment of the first layer 2 um or less, a satisfactory coating film exterior is obtained.
The mean particle diameter of the pigment of the second layer is preferably 0.05 um or more but less than ⅓ of the wavelength of the specific color in order to selectively allow light of the wavelength of the specific color to be transmitted. In addition, the laminated coating film structure is particularly effective for rendering a chromatic color.
In a preferable embodiment, an electrodeposited coating film is formed on the surface of the coated object, and a coating film of the first layer is formed to as to be directly layered on the surface of the electrodeposited coating film. In addition, in a more preferable embodiment, a coating film of the second layer is formed to as to be directly layered on the surface of the coating film of the first layer. However, a laminated coating film structure provided with a coating film such as an intermediate coating film other than the coating films of the first layer and the second layer is also included in the present invention provided that this intermediate coating film and the like is not involved in the ultimate coating film color, and the specific color is exclusively demonstrated by both coating films of the first layer and the second layer.
This laminated coating film configuration has the characteristics indicated below. First, there is no intermediate coating film like that of the laminated coating film structure shown in
The following provides a detailed explanation.
<Electrodeposited Coating Film 2>
The electrodeposited coating film 2 can be precipitated and formed on the side of the coated object 1 by immersing the coated object 1 in a cationic electrodeposition coating material, using the coated object 1 as an anode and using an electrode plate within the electrodeposition tank as a cathode, and applying a direct current there between. The cationic electrodeposition coating material contains a cationic epoxy resin, curing agent, pigment and additives.
The cationic epoxy resin contains an amine-modified epoxy resin. Examples of epoxy resins that can be used include those modified with a polyester polyol, polyether polyol or alkyl phenol, as well as those in which chain length of the epoxy resin has been extended.
Examples of curing agents that can be used include block isocyanates obtained by blocking a polyisocyanate with a blocking agent. Examples of polyisocyanates include aliphatic, alicyclic and aromatic-aliphatic polyisocyanates. Examples of blocking agents include lactam-based blocking agents such as ε-caprolactam and oxime-based blocking agents such as formaldoxime.
The electrodeposition coating material typically contains pigment as coloring agent. Examples of coloring pigments include titanium oxide, carbon black and iron oxide, examples of extender pigments include kaolin, talc, aluminum silicate, calcium carbonate, mica and clay, and examples of rust preventive pigments include zinc phosphate, iron phosphate, aluminum phosphate, calcium phosphate, zinc oxide, aluminum tripolyphosphate, zinc molybdate, aluminum molybdate and calcium molybdate. The amount of pigment can be within the range of 10 to 30% by weight based on the solid component of the electrodeposition coating material composition.
<Base Coating Film 3>
The base coating film 3 can be formed by coating an aqueous base coating material or oily (solvent-based) base coating material. With respect to an aqueous base coating material, acrylic resin, polyester resin, polyurethane resin or vinyl resin and the like can be used for the aqueous resin serving as the main component thereof.
The acrylic resin is composed of an acrylic emulsion or water-soluble acrylic resin and the like. The acrylic emulsion is produced by emulsion polymerization, suspension polymerization or diffusion polymerization and the like using a polymerizable unsaturated monomer. Examples of polymerizable unsaturated monomers include hydroxyl group-containing polymerizable unsaturated monomers, carboxyl group-containing polymerizable unsaturated monomers, aminoalkyl acrylates, aminoalkyl methacrylates, acrylamides, methacrylamides and derivatives thereof, sulfoalkyl acrylates, polyvinyl compounds, and ultraviolet-absorbing or ultraviolet-stabilizing polymerizable unsaturated monomers.
Examples of water-soluble acrylic resins include carboxyl group-containing polymerizable unsaturated monomers and nonionic polymerizable unsaturated monomers having a polyoxyalkylene chain. Examples of carboxyl group-containing polymerizable unsaturated monomers include examples of polymerizable unsaturated monomers of the previously described acrylic emulsions. Examples of nonionic polymerizable unsaturated monomers having a polyoxyalkylene chain include polyethylene glycol acrylate, polyethylene glycol methacrylate, polypropylene glycol acrylate and polypropylene glycol methacrylate.
Water solubility or water dispersibility is imparted to the polyester resin by neutralizing the carboxyl groups with a basic neutralizing agent. Examples of carboxyl group-containing polyester resins include those obtained by esterifying a polybasic acid component and a polyvalent alcohol component under conditions such that the carboxyl groups are in excess with respect to the hydroxyl groups, and those obtained by reacting an acid anhydride with a polyester polyol obtained by reacting a polybasic acid component and a polyvalent alcohol component under conditions such that the hydroxyl groups are in excess with respect to the carboxyl groups. Examples of the basic neutralizing agents include inorganic bases and amines.
Pigment is added to the aqueous base coating material as coloring agent. Examples of coloring agents include organic pigments such as azochelate pigments, insoluble azo pigments, condensed azo pigments, diketopyrrolopyrolle pigments, benzoimidazolone pigments, phthalocyanine pigments, indigo pigments, perinone pigments, perylene pigments, dioxane pigments, quinacridone pigments, isoindolinone pigments or metal complex pigments, and inorganic pigments such as chrome yellow, yellow iron oxide, red iron oxide, carbon black and titanium dioxide. Moreover, an extender pigment such as calcium carbonate, barium sulfate, clay or talc, or an iridescent pigment, may also be used in combination.
A coating material additive such as a crosslinking agent, flat pigment, curing catalyst, thickener, organic solvent, basic neutralizing agent, ultraviolet absorber, photostabilizer, surface conditioner, antioxidant or silane coupling agent can be incorporated in the aqueous base coating material as necessary.
A crosslinking agent is a compound capable of forming a cured coating film by reacting with a crosslinking functional group such as a hydroxyl group, carboxyl group or epoxy group in an aqueous resin, and examples of crosslinking agents include melamine resin, polyisocyanate compounds, blocked polyisocyanate compounds, epoxy group-containing compounds, carboxyl group-containing compounds and carbodiimide group-containing compounds.
The aqueous base coating material can be coated onto the electrodeposited coating film 2 of the coated object 1 by, for example, air spray coating, airless spray coating, rotary atomization coating or curtain coating, and static electricity may be applied. The first base coating film 3a and the second base coating film 3b are respectively coated to a dry film thickness of 8 to 12 um. After coating, the coating films may be pre-heated for about 1 to 15 minutes at about 40 to 100 degrees Celsius in order to evaporate moisture present in the coating films.
<Clear Coating Film 4>
Although there are no particular limitations on the resin used to form the clear coating film, examples include combinations of acrylic resin and/or polyester resins and amino resins, and acrylic resins and/or polyester resins having a carboxylic acid-epoxy curing system. For example, a two-liquid urethane clear coating material contains a hydroxyl group-containing acrylic resin and a polyisocyanate compound. Examples of organic solvents include hydrocarbon-based solvents, ester-based solvents, ketone-based solvents, alcohol-based solvents, ether-based solvents and aromatic petroleum-based solvents.
A pigment, non-water-dispersible resin, polymer fine particles, curing catalyst, ultraviolet absorber, photostabilizer, coated surface conditioner, antioxidant, fluidity conditioner or wax and the like can be suitably contained in the clear coating material as necessary. Examples of curing catalysts include organic tin compounds, triethylamine and diethanolamine. Examples of ultraviolet absorbers include benzophenone, benzotriazole, cyanoacrylate, salicylate and anilide oxalate-based compounds, as well as ultraviolet stabilizers such as hindered amine compounds.
The clear coating material can be coated onto the base coating film 3 by airless spraying, air spraying or a rotary atomization coater and the like, and static electricity may be applied during coating. After coating to a dry film thickness of 35 to 40 um, the coating film is cured by heating for 20 minutes at 140 degrees Celsius.
<Pigment of Base Coating Film>
As was previously explained, light absorption and reflection properties differ according to particle diameter of the pigment even for the same coloring pigment. Namely, when light of the wavelength of a specific color propagates through a coating film, in plain terms, the light passes between the pigment particles. Light of the wavelength of a specific color passes through more easily the smaller the particle diameter of the pigment (good transmission). During the course of passing between the pigment particles, unnecessary wavelengths of light other than that of the specific color are absorbed by the pigment (chroma increases). On the other hand, as particle diameter of the pigment increases, it becomes more difficult for light of the wavelength of a specific color to pass between the pigment particles. Namely, the light is more easily reflected by the surface of the pigment particles (good reflectivity).
The present invention serves to increase chroma by enhancing transmission of light of a specific color in the upper second base coating film 3b, and serves to increase lightness by enhancing reflectivity of light of a specific color in the lower first base coating film 3a. Consequently, in the present invention, pigment particle diameter is optimized for the first base coating film 3a and the second base coating film 3b, respectively.
<<Pigment Particle Diameter of Second Base Coating Film 3b>>
An explanation is first provided of optimization of pigment particle diameter of the second base coating film 3b.
C*ab=[(a*)2+(b*)2]1/2
The samples were prepared by sequentially carrying out electrodeposition coating (main component: epoxy resin, coating film thickness: 18 um), first base coating (aqueous, main component: acrylmelamine resin, coating film thickness: 10 um), second base coating (aqueous, main component: acrylmelamine resin, coating film thickness: 10 um) and clear coating (main component: acrylurethane resin, coating film thickness: 35 um) on a steel plate. The pigment concentrations of the first base coating film 3a and the second base coating film 3b were both 30% by weight. The mean particle diameter of the pigment of the first base coating film 3a was 0.4 um.
According to
delta E*ab=[(delta L*)2+(delta a*)2+(delta b*)2]1/2
According to
On the basis of the above, from the viewpoint of increasing the chroma of rendered colors, the mean particle diameter of the pigment of the second base coating film 3b was determined to preferably less than ½ and more preferably less than ⅓ the wavelength of a specific color. In addition, from the viewpoint of weather resistance, the mean particle diameter of the second base coating film 3b was determined to preferably be 0.05 um or more.
<<Pigment Particle Diameter of First Base Coating Film 3a>>
The following provides an explanation of optimization of the pigment particle diameter of the lower first base coating film 3a.
According to
Here, a high reflection rate of light according to the pigment color of the first base coating film 3a means that the amount of light of that pigment color that is absorbed by the electrodeposited coating film 2 beneath the first base coating film 3a is small, and thus, color rendering of high lightness is obtained.
On the basis of the above, it can be said that, from the viewpoint of improving lightness of color rendering, the mean particle diameter of pigment of the first base coating film 3a is preferably ½ or more of the wavelength of a specific color, and from the viewpoint of smoothness of the coating film surface, the mean particle diameter is preferably 2 um or less and particularly preferably 0.5 um or less.
Furthermore, volume mean particle diameter is used for the mean particle diameter. Volume mean particle diameter can be measured using laser diffraction or centrifugal sedimentation and the like. More specifically, measurement using laser diffraction can be carried out by, for example, using a laser diffraction particle analyzer (MT3300EXII Microtrack Particle Size Distribution Analyzer manufactured by Nikkiso Co., Ltd.) that complies with JIS Z 8825-1 (laser diffraction for particle size analysis). If measurement is carried out using this device, the particles to be measured (pigment) are first irradiated with a laser to obtain a scattering pattern of the laser light. The volume distribution of the measured particles can then be obtained from the resulting scattering pattern by using data indicating the correlation between the scattering pattern and the volume distribution of spherical particles.
Furthermore, volume distribution can be converted to number distribution by carrying out prescribed arithmetic processing using software, for example. In the case the measured particles are particles having the same specific gravity such as single pigment particles, the particles can be assumed to be spherical, and volume distribution and number distribution have nearly the same distribution. For example, with respect to the distributions shown in
<Evaluation of Laminated Coating Film Performance>
The ordinary pigment A of a particle size distribution having a peak at 0.25 um, a highly reflective pigment B of a particle size distribution having a peak at 0.35 um (mean particle diameter: 0.35 um), and a high chroma pigment C of a particle size distribution having a peak at 0.11 um (mean particle diameter: 0.11 um) were prepared for use as pigments of the base coating film, as shown in
A total Of 16 types of samples were prepared having different compositions for the base coating film 3 by combining the first base coating materials (4 types) and the second base coating Materials (4 types). All the samples were composed by laminating a first base coating film, a second base coating film and a clear coating film consisting of an acrylurethane coating material on an epoxy-based electrodeposited coating film on the surface of a steel plate (without an intermediate coating). After sequentially carrying first base coating and second base coating on the electrodeposited coating film and preheating, clear coating was carried out followed by baking for 20 minutes at 140 degrees Celsius. The thicknesses of the coating films were 18 um for the electrodeposited coating film, 10 um for the first base coating film and second base coating film, and 35 um for the clear coating film. In addition, the lightness (L*) of the electrodeposited coating film was 50 plus or minus 3. Furthermore, lightness (L*) refers to color brightness and an example thereof is a value obtained in compliance with JIS Z 8729. In addition, lightness (L*) demonstrates a high correlation with light reflection rate when light is radiated onto an object.
In addition, a reference sample was prepared to evaluate the performance of the laminated coating films of each of the samples. The reference sample employed a composition in which an intermediate coating film using a white pigment (main component: polyester melamine resin), an oily base coating film using ordinary pigment A (main component: acrylmelamine resin), and a clear coating film (main component: acid epoxy-curable acrylic resin) were laminated onto an epoxy-based electrodeposited coating film on the surface of a steel plate. The thicknesses of the coating films were 18 um for the electrodeposited coating film, 25 um for the intermediate coating film, 10 um for the base coating film and 35 um for the clear coating film. In addition, the pigment concentration of the intermediate coating film was 45% by weight, and the pigment concentration of the base coating film was 30% by weight.
The color difference (delta E*) between the 16 types of samples and the reference sample was measured using the GSP-2 color difference meter manufactured by Murakami Color Research Laboratory at an incidence angle of 45 degrees and an acceptance angle of −80 to 80 degrees (variable angle: 5 degrees). The results are shown in
Here, the reference sample corresponds to a conventional product, and since it has an intermediate coating film of white pigment, even though ordinary pigment A is used for the base coating film, red color is vividly rendered by the laminated coating film. In contrast, since the 16 types of samples do not have an intermediate coating film, they are correspondingly disadvantageous in terms of rendering a vivid red color.
According to
In contrast, line 2-4 of
In sample Y (combination of first base coating material 1-4 and second base coating material 2-4), in which the highly reflective pigment B was used for the pigment of first base coating film and the high chroma pigment C was used for pigment of the second base coating film, color difference (delta E*) was less than 1.5, thus demonstrating that vivid color rendering is obtained that is comparable to that of the reference sample.
<Case of Pigments of Other Colors>
The results of the studies described above were obtained by examining color rendering using red color having a peak wavelength of 660 nm as the specific color with the first base coating film and the second base coating film. Therefore, the following provides an explanation of pigment particle diameter in the case of generating other colors as specific colors with both base coating films. In this case as well, the mean particle diameter of the pigment can be determined based on the peak wavelength of that specific color in the same manner as in the case of red pigment. Namely, the same study is conducted with the exception of changing the pigment particle diameter. The following indicates examples of this.
In the case of rendering blue color having a peak wavelength of 450 nm, the mean particle diameter of the blue pigment of the first base coating film is 0.225 to 2 um, and the mean particle diameter of the blue pigment of the second base coating film is 0.05 to less than 0.225 um.
In the case of rendering green color having a peak wavelength of 550 nm, the mean particle diameter of the green pigment of the first base coating film is 0.275 to 2 um, and the mean particle diameter of the green pigment of the second base coating film is 0.05 to less than 0.275 um.
In the case of rendering yellow color having a peak wavelength of 580 nm, the mean particle diameter of the yellow pigment of the first base coating film is 0.290 to 2 um, and the mean particle diameter of the yellow pigment of the second base coating film is 0.05 to less than 0.290 um.
Although the present description discloses various aspects of technology as has been previously described, the primary technology there within is summarized below.
One aspect of the present invention is a laminated coating film structure having a laminated coating film that renders a specific color on a coated object, wherein the laminated coating film is provided with a first layer arranged on the side close to the coated object and containing a pigment in which the mean particle diameter is ½ or more the wavelength of the specific color but 2 um or less, and a second layer arranged on the side far from the coated object and containing a pigment in which the mean particle diameter is 0.05 um or more but less than ½ the wavelength of the specific color.
According to this configuration, in the laminated coating film structure in which a specific color is made to be rendered by both coating films of a first layer on the side close to the coated object and a second layer on the side far from the coated object, satisfactory color rendering can be obtained without particularly increasing the thickness of the coating films.
In addition, the laminated coating film structure is made to render the specific color with both coating films of the first layer and the second layer.
In addition, in the laminated coating film structure, the mean particle diameter of the pigment contained in the second layer is preferably 0.05 um or more but less than ⅓ the wavelength of the specific color.
According to this configuration, even better color rendering can be obtained.
In addition, in the laminated coating film structure, the specific color is preferably a chromatic color. By adjusting the particle diameters of the pigments contained in each of the first layer and the second layer, the effect of allowing the obtaining of satisfactory color rendering can be more effectively demonstrated without particularly increasing the thickness of the coating films.
In addition, in the laminated coating film structure, the second layer is preferably in direct contact with the first layer.
In addition, in the laminated coating film structure, an electrodeposited coating film is preferably provided between the coated object and the first layer.
In addition, in the laminated coating film structure, the first layer is preferably in direct contact with the electrodeposited coating film.
Although the present invention has been fully described by way of example with reference to the accompanying drawings, it is to be understood that various changes and modifications will be apparent to those skilled in the art. Therefore, unless otherwise such changes and modifications depart from the scope of the present invention hereinafter defined, they should be construed as being included therein.
According to the present invention, a laminated coating film structure can be obtained that allows the obtaining of vivid coloring without particularly increasing the thickness of coating films, while also having favorable weather resistance and appearance of the coating film.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2010-114595 | May 2010 | JP | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2011/002665 | 5/13/2011 | WO | 00 | 10/19/2012 |
