COLOR-TREATED BASE MATERIAL AND BASE MATERIAL COLOR TREATMENT METHOD THEREFOR

Abstract

 This color-treated base material, which comprises a matrix comprising magnesium, a film formed on the matrix and containing a compound represented by chemical formula 1, and a wavelength conversion layer formed on the film, can improve the durability of the base material while maintaining the unique metal texture and gloss of the base material and can uniformly realize various colors, such as blue and green, including an achromatic color such as black, on the surface of the base material and thus can be usefully used in the fields of building exterior materials, automobile interiors, and particularly electrical/electronic component materials, such as mobile product frames, in which a metal material is used.

Description

[Technical Field]

[0001] The present invention relates to a color-treated substrate and a substrate color treatment method therefor.

[Background Art]

[0002] Magnesium is a metal which belongs to lightweight metals among practical metals, has excellent wear resistance, and is very resistant to sunlight and eco-friendly, but has a difficulty in realizing a metal texture and various colors. Further, since it is a metal having the lowest electrochemical performance and is highly active, when a color treatment is not performed thereon, it may be quickly corroded in air or in a solution, and thus has a difficulty in industrial application.

[0003] Recently, the magnesium industry has been receiving attention due to the weight reduction trend in overall industry. As exterior materials with a metal texture has become trendy in the field of electrical and electronic component materials such as mobile product frames, research to resolve the above-described problem of magnesium is being actively carried out.

[0004] As a result, Korean Patent Laid-open Publication No. 2011-0016750 disclosed a PVD-sol gel method of performing sol-gel coating after dry coating a surface of a substrate formed of a magnesium alloy with a metal-containing material in order to realize a metal texture and ensure corrosion resistance, and Korean Patent Laid-open Publication No. 2011-0134769 disclosed an anodic oxidation method of imparting gloss to a surface of a substrate including magnesium using chemical polishing and coloring a surface by anodic oxidation of the substrate in an alkaline electrolyte including a pigment dissolved therein.

[0005] However, the PVD-sol gel method has a problem in that a texture realized on the surface of the substrate is not the intrinsic texture of magnesium although a metal texture may be realized on the surface of the substrate, and the realization of a variety of colors is difficult. Furthermore, when a color treatment is performed using the anodic oxidation method, there is a problem in that an opaque oxide film is formed on the surface of the substrate, and the realization of the intrinsic texture of metals is not easy.

[0006] Further, products formed of a metal material which is color-treated to have a black color have become popular according to various needs of the recent consumer and the trend of high-quality fashion. To this end, a technique to realize a diversity of colors, especially a black color on the surface of the material is desperately needed.

[0007] Accordingly, there is an urgent need for the development of a color treatment technique to maintain an intrinsic texture and gloss of metals and improve durability as well as to realize a diversity of colors including an achromatic color such as a black color on a surface.

[Disclosure]

[Technical Problem]

[0008] An objective of the present invention is to provide a substrate which maintains a texture and gloss of metals and has a surface color-treated to have a variety of colors including a black color.

[0009] Another objective of the present invention is to provide a method of color-treating the substrate.

[Technical Solution]

[0010] In order to achieve the objectives, one embodiment of the present invention provides a color-treated substrate, including:

a matrix containing magnesium;

a film formed on the matrix and containing a compound represented by the following Chemical Formula 1; and

a wavelength conversion layer formed on the film:

        [Chemical Formula 1]     M(OH)_m

where M includes one or more selected from the group consisting of Na, K, Mg, Ca and Ba, and m is 1 or 2,
wherein a condition of the following Expression 1 is satisfied with respect to an arbitrary point A existing on the wavelength conversion layer:

where T_film represents an average thickness of the film at the point A, T_ML represents an average thickness of the wavelength conversion layer at the point A.

[0011] Further, another embodiment of the present invention provides a method of color-treating a substrate, including: a step of forming a film on a matrix containing magnesium; and
a step of forming a wavelength conversion layer on the film, wherein a condition of the following Expression 1 is satisfied with respect to an arbitrary point A existing on the wavelength conversion layer:

where T_film represents an average thickness of the film at the point A, T_ML represents an average thickness of the wavelength conversion layer at the point A.

[Advantageous Effects]

[0012] The color-treated substrate according to the present invention can maintain a texture and gloss of metals, improve durability of a substrate and uniformly realize a variety of colors including a blue color, a green color, an achromatic color such as a gray color, a black color or the like on a surface of the substrate, and thus can be usefully used in the fields of building exterior materials, automobile interiors, and particularly electrical and electronic component materials, such as mobile product frames, in which a metal material is used.

[Description of Drawings]

[0013] 

FIG. 1 is an image taken by a transmission electron microscope (TEM), which shows a film and a wavelength conversion layer of a color-treated substrate obtained in an example.

FIG. 2 is an image taken by a transmission electron microscope (TEM), which shows a film and a wavelength conversion layer of a color-treated substrate obtained in another example.

[Best Mode for Carrying out the Invention]

[0014] While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and will herein be described in detail. It should be understood, however, that there is no intent to limit the invention to the particular forms disclosed, but on the contrary, the invention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention.

[0015] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms "a," "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises," "comprising," "includes" and/or "including," when used herein, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.

[0016] "Color coordinates", as used herein, refer to coordinates in a CIE color space, including color values defined by the Commission International de l'Eclairage (CIE), and any position in the CIE color space may be expressed as three coordinate values of L*, a* and b*.

[0017] Here, an L* value represents brightness. L*=0 represents a black color, and L*=100 represents a white color. Moreover, an a* value represents whether a color at a corresponding color coordinate leans toward a pure magenta color or a pure a green color, and a b* value represents whether a color at a corresponding color coordinate leans toward a pure yellow color or a pure a blue color.

[0018] Specifically, the a* value ranges from -a to +a, the maximum a* value (a* max) represents a pure magenta color, and the minimum a* value (a* min) represents a pure a green color. For example, when an a* value is negative, a color leans toward a pure a green color, and when an a* value is positive, a color leans toward a pure magenta color. This indicates that, when a*=80 is compared with a*=50, a*=80 represents a color which is closer to a pure magenta color than a*=50. Furthermore, the b* value ranges from -b to +b. The maximum b* value (b* max) represents a pure yellow color, and the minimum b* value (b* min) represents a pure a blue color. For example, when a b* value is negative, a color leans toward a pure blue color, and when a b* value is positive, a color leans toward a pure a yellow color. This indicates that, when b*=50 is compared with b*=20, b*=80 represents a color which is closer to a pure yellow color than b*=50.

[0019] Further, a "color deviation" or a "color coordinate deviation", as used herein, refers to a distance between two colors in the CIE color space. That is, a longer distance denotes a larger difference in color, and a shorter distance denotes a smaller difference in color, and this may be expressed by ΔE* represented by the following Expression 5:

[0020] In addition, a "black" color, as used herein, refers to a color of which an average color coordinate (L*) with respect to brightness based on CIE color coordinates is 60 or less. For example, the black color may include an achromatic color such as a black color, a grey color or the like, and a black rust color or a black navy color or the like mixed with a green-based color or a blue-based color.

[0021] Moreover, a "blue" color, as used herein, refers to a color in which L* is more than 60 and b* is less than 5 in average color coordinates (L*, a*, b*) based on CIE color coordinates. As described above, since b* represents a pure yellow or a blue color, the blue color refers to a color having a low b* value, and specifically, a color having a b* value of less than 5 in the present invention. Further, although color coordinates of a* is not particularly limited, the a* may be 20 or less, 15 or less, 10 or less, or 5 or less. Examples of the blue color according to the present invention may include a navy color; a blue color; a light blue color; or a cyan color mixed with a green-based color and the like, which are included in the range of the color coordinates.

[0022] Further, a "green" color, as used herein, refers to a color in which L* is more than 60, a* is -5 or less and b* is 5 or more in average color coordinates (L*, a*, b*) based on CIE color coordinates. Since a* represents pure magenta and a green colors in a CIE color space, the green color refers to a color having a negative a* value, specifically, a color having an a* value of -5 or less, and more specifically, a color having an a* value of -6 or less, or -7 or less in the present invention. Further, coordinates of b* of the green color may be 5 or more, and specifically, 6 or more or 7 or more. Examples of the green color according to the present invention may include a yellow-green color; a pale blue-green color, an iron blue color, a green color or the like, which are included in the range of the color coordinates.

[0023] Furthermore, a "wavelength conversion layer", as used herein, refers to a layer, including intercalation interface on the surface of the film, for controlling a wavelength of incident light by adjusting reflection, refraction, scattering, diffraction or the like of light, which may serve to minimize additional refraction and/or scattering, in a top coat, of light refracted and/or scattered in a film, and maintain a color developed by the layer by inducing light reflection.

[0024] Lastly, a unit "T", as used herein, represents a thickness of a substrate including magnesium, and is the same as a unit "mm".

[0025] The present invention provides a color-treated substrate and a substrate color treatment method therefor.

[0026] A PVD-sol gel method, an anodic oxidation method or the like, which is a method of coating a surface of a material with a metal-containing material, a pigment or the like, has been conventionally known as a method for realizing a color on the material including magnesium. However, these methods may cause a reduction in durability of the substrate. Further, it is difficult to realize a uniform color on the surface of the material, and there is a problem of unmet reliability because a coated film layer is easily detached. Moreover, products formed of a metal material which is color-treated to have a black color have become popular according to various needs of the recent consumer and the trend of high-quality fashion. To this end, there is an increasing need for a technique to realize a black color on the surface of the material.

[0027] Accordingly, the present invention suggests a substrate which maintains a texture and gloss of metals and is color-treated to have a variety of colors including a black color, and a method of color-treating the substrate.

[0028] The color-treated substrate according to the present invention may maintain a texture and gloss of metals, improve durability of a substrate and uniformly realize a variety of colors including an achromatic color such as a gray color, a black color or the like on a surface of the substrate by including a nanometer scale film and a wavelength conversion layer which have a specific ratio on the substrate, and thus may be usefully used in the fields of building exterior materials, automobile interiors, and particularly electrical and electronic component materials, such as mobile product frames, in which a metal material is used.

[0029] Hereinafter, the present invention will be described in detail.

[0030] An embodiment of the present invention provides a color-treated substrate, including:

a matrix containing magnesium;

a film formed on the matrix and containing a compound represented by the following Chemical Formula 1; and

a wavelength conversion layer formed on the film:

        [Chemical Formula 1]     M(OH)_m

where M includes one or more selected from the group consisting of Na, K, Mg, Ca and Ba, and m is 1 or 2,
wherein a condition of the following Expression 1 is satisfied with respect to an arbitrary point A existing on the wavelength conversion layer:

where T_film represents an average thickness of the film at the point A, T_ML represents an average thickness of the wavelength conversion layer at the point A.

[0031] Specifically, the substrate satisfies the condition of the following Expression 1 as follows: 0.1 to 10; 0.1 to 9; 0.1 to 8.5; 0.5 to 6; 0.5 to 4; or 1 to 8.5.

[0032] The color-treated substrate according to the present invention may have a structure in which the film and the wavelength conversion layer are sequentially stacked on the matrix containing magnesium, and this stacked structure may be formed on one or both surfaces of a metal matrix. Further, the substrate may prevent a decrease in the light transmittance of the wavelength conversion layer as well as uniformly develop a color on the surface by satisfying the condition of Expression 1. Here, examples of the developed color may include an achromatic color such as a grey color, a black color or the like as well as a blue color, a green color, etc.

[0033] In the color-treated substrate according to an embodiment, when an average thickness ratio T_film/T_ML of the film to the wavelength conversion layer at an arbitrary point A existing on the wavelength conversion layer is in the range of 0.1 to 6.0, an achromatic color such as a black color, a grey color or the like may be developed. In this case, L* of average color coordinates of any three points included in an arbitrary area with a width of 1 cm and length of 1cm existing on the wavelength conversion layer may be 60 or less. Further, the average thickness of the film may be less than 80 nm, and specifically, may be 75 nm or less, 70 nm or less, 65 nm or less, 60 nm or less; 50 nm or less, 10 to 55 nm or 25 to 55 nm (refer to Experimental Example 2).

[0034] In the color-treated substrate according to another embodiment, when an average thickness ratio T_film/T_ML of the film to the wavelength conversion layer with respect to an arbitrary point A existing on the wavelength conversion layer is in the range of 0.2 to 4.0, a blue-based color such as a blue color, a cyan color, a sky blue color or the like may be developed. In this case, L* is more than 60 and b* is less than 5 in average color coordinates of any three points included in an arbitrary area with a width of 1 cm and length of 1cm existing on the wavelength conversion layer. Further, the average thickness of the film may be in the range of 80 to 140 nm, and specifically, may be 80 to 100 nm, 120 to 140 nm, 110 to 130 nm, 100 to 135 nm or 85 to 135 nm (refer to Experimental Example 2).

[0035] In the color-treated substrate according to still another embodiment, when an average thickness ratio T_film/T_ML of the film to the wavelength conversion layer with respect to an arbitrary point A existing on the wavelength conversion layer is in the range of 0.7 to 8.5, a green-based color such as a yellow-green color; a pale blue-green color, an iron blue color, a green color or the like may be developed. In this case, L* is more than 60, a* is -5 or less and b* is 5 or more in average color coordinates of any three points included in an arbitrary area with a width of 1 cm and length of 1cm existing on the wavelength conversion layer. Further, the average thickness of the film may be more than 140 nm and 300 nm or less, and specifically, may be 145 nm to 300 nm, 146 nm to 290 nm, 147 nm or more to 260 nm, 145 nm to 200 nm or 145 nm to 170 nm (refer to Experimental Example 2).

[0036] Hereinafter, each component of the color-treated substrate according to the present invention will be described in further detail.

[0037] First, the matrix containing magnesium serves to define a basic framework and physical properties of a substrate, and may be regarded as a form before the color-treated substrate according to the present invention is subject to a color treatment.

[0038] Here, the type or form of the matrix containing magnesium is not particularly limited as long as it is usable as a frame in the fields of electrical and electronic component materials. As an example, a magnesium substrate formed of magnesium; a stainless steel or titanium (Ti) substrate of which a surface has magnesium dispersed therein or the like may be used as the matrix.

[0039] Next, the film is formed on the surface of the matrix and functions to scatter or refract light incident to the surface.

[0040] Here, the film is not particularly limited as long as it is a transparent film which allows light to be transmitted and may refract or scatter incident light. For example, the film may include one or more of sodium hydroxide (NaOH), potassium hydroxide (KOH), magnesium hydroxide (Mg(OH)₂), calcium hydroxide (Ca(OH)₂) and barium hydroxide (Ba(OH)₂), and more specifically, may include magnesium hydroxide (Mg(OH)₂).

[0041] Further, the film develops a variety of colors such as an achromatic color such as a black color, a grey color, and a blue color, a green color or the like on the substrate by having a specific average thickness ratio with the wavelength conversion layer formed on the film, and here, the film may serves as a color-developing layer which defines a developed color. For example, in the color-treated substrate according to the present invention, when the average thickness ratio of the film and the wavelength conversion layer is the same while the average thickness of the film formed on the matrix is different, a color developed on the surface may be different. Here, the average thickness of the film is not particularly limited as long as it is a nanometer scale thickness. Specifically, the average thickness of the film may be in the range of 500 nm or less, 400 nm or less, 300 or less, 100 nm to 250 nm, 10 to 75 nm, 50 to 140 nm, 140 to 200 nm, or 1 to 300 nm.

[0042] Next, the wavelength conversion layer is formed on the film and includes an intercalation interface on the surface of the film, and thus scatters and/or refracts light which is refracted and/or scattered in the film; and light reflected on the surface of the matrix again to develop a color on the surface of the matrix.

[0043] Here, as described above, the wavelength conversion layer has to have an average thickness ratio with the film, which satisfies the condition of Expression 1, and have a nanometer scale average thickness in order to develop a color on the surface of the matrix. Specifically, the average thickness of the wavelength conversion layer may be 200 nm or less. More specifically, the average thickness may be 190 nm or less; 180 nm or less; 170 nm or less; 160 nm or less; or 150 nm or less. The failure of coloring due to a decrease in the light transmittance of the wavelength conversion layer may be prevented by adjusting the average thickness of the wavelength conversion layer to within the above-described range in the present invention. Moreover, the component or form of the wavelength conversion layer is not particularly limited. As an example, the wavelength conversion layer may include one or more selected from the group consisting of metals including aluminum (Al), chromium (Cr), titanium (Ti), gold (Au), molybdenum (Mo), silver (Ag), manganese (Mn), zirconium (Zr), palladium (Pd), platinum (Pt), cobalt (Co), cadmium (Cd) or copper (Cu) and ions thereof, and specifically, may include chromium (Cr). Further, the metals may be in the form of metal particles, and may include various types such as a metal nitride, a metal oxide, a metal carbide or the like by reacting with a nitrogen gas, an ethane gas, an oxygen gas and the like in the process of forming the wavelength conversion layer. Moreover, the wavelength conversion layer may be a continuous layer in which the metals are densely stacked on the film and fully cover the surface of the film, or a discontinuous layer in which the metals are dispersed on the film, but is not limited thereto.

[0044] Further, the color-treated substrate according to the present invention may further include a top coat formed on the wavelength conversion layer in order to improve scratch resistance and durability of the surface of the substrate.

[0045] Here, a clear coating agent for forming the top coat is not particularly limited as long as it is a clear coating agent which is applicable to metal coatings. More specifically, a matte clear coating agent or a glossy/matte clear coating agent which is applicable to metal coatings or the like may be exemplified. Further, the top coat may have an excellent adhesiveness with the wavelength conversion layer. Specifically, when the color-treated substrate including the top coat was sprayed with 5 wt% salt water at 35 °C and the adhesiveness thereof was evaluated after 72 hours, the top coat may have a peel rate of 5% or less.

[0046] In an embodiment, the color-treated substrate having a matte or glossy/matte top coat formed thereon was sprayed with 5 wt% salt water at 35 °C and was tested by a cross-cut tape test method after 72 hours. As a result, it was determined that the area of the peeled top coat was 5% or less with respect to the total area of the sample. As can be seen from the results, the substrate having the top coat formed thereon according to the present invention has excellent adhesiveness between the color-treated substrate and the top coat (refer to Experimental Example 3).

[0047] Furthermore, an embodiment of the present invention provides a method of color-treating a substrate, including: a step of forming a film on a matrix containing magnesium; and a step of forming a wavelength conversion layer on the film, wherein the condition of the following Expression 1 is satisfied with respect to an arbitrary point A existing on the wavelength conversion layer:

where T_film represents an average thickness of the film at the point A, T_ML represents an average thickness of the wavelength conversion layer at the point A.

[0048] In the method of color-treating the substrate according to the present invention, a diversity of colors such as an achromatic color such as a black color, a grey color or the like as well as a blue color, a green color or the like may be uniformly developed on a surface of a substrate by forming a nanometer scale film and wavelength conversion layer having a specific ratio in the range of 0.1 to 10.

[0049] The step of forming the film may be performed by immersing the matrix containing magnesium in a hydroxide solution in the color treatment method.

[0050] Here, any solution including a hydroxyl group (-OH group) may be used as the hydroxide solution, without particular limitation. Specifically, a solution having one or more selected from the group consisting of NaOH, KOH, Mg(OH)₂, Ca(OH)₂ and Ba(OH)₂ dissolved therein may be used. The hydroxide solution has an advantage in that the film is uniformly formed on the surface of the substrate in a short time and a developed color has excellent coloring power and clarity (refer to Experimental Example 1).

[0051] Further, the preparation method according to the present invention may control the thickness of the film formed on the surface of the matrix according to immersion conditions. Here, since the amount of heat conduction of the matrix varies depending on the thickness of the matrix, when the thicknesses of the matrices are different, the thickness of the films formed on matrices may be different even though the matrices were immersed under the same conditions. Accordingly, it is preferable to control the thickness of the film by adjusting immersion conditions according to the thickness of the matrix containing magnesium.

[0052] As an example, when the thickness of the matrix containing magnesium is in the range of 0.4 to 0.7 T, the temperature of the hydroxide solution may be in the range of 15 to 200 °C, and specifically, 15 to 50 °C, 15 to 30 °C, 90 to 150 °C, or 95 to 110 °C. Further, the immersion time of the matrix may be 60 minutes or less, and specifically, may be 50 minutes or less, 40 minutes or less, 30 minutes or less, 20 minutes or less, or 15 minutes or less. Further, the concentration of the hydroxide solution may be in the range of 1 to 80 wt%, and specifically, may be in the range of 1 to 70 wt%; 5 to 50 wt%; 10 to 20 wt%; 1 to 40 wt%; 30 to 60 wt%; 15 to 45 wt% or 5 to 20 wt%. In the color treatment method, the film may be uniformly formed in a short time and a decrease in the intrinsic glossiness of metals due to an excessively increased thickness of the film may be prevented by immersing the matrix in the above-described condition ranges.

[0053] Moreover, the step of forming the wavelength conversion layer in the color treatment method may be performed using a method which is generally used in the related field without particular limitation. As a specific example, it may be performed by a method such as vacuum deposition, sputtering, ion plating, ion beam deposition or the like.

[0054] Further, the method of color treating the substrate according to the present invention substrate may further include one or more steps of: pretreating the surface of the matrix before the step of forming the film; and rinsing after the step of forming the film.

[0055] Here, the step of pretreating the surface is a step of eliminating contaminants remaining on the surface by treating the surface using an alkaline cleaning solution or grinding the surface before forming the film on the matrix. Here, the alkaline cleaning solution is not particularly limited as long as the solution is generally used to clean a surface of metals, metal oxides or metal hydroxides in the related field. Further, the grinding may be performed by buffing, polishing, blasting, electrolytic polishing or the like, but is not limited thereto. In the present step, not only contaminants or scale which is present on the surface of the matrix containing magnesium may be removed, but also the speed of forming the film may be controlled by surface energy of the surface and/or surface conditions, specifically, microstructural changes of the surface. That is, the thickness of the film formed on the polished matrix may be different from that of the film formed on the unpolished matrix even though the film is formed on the polished matrix under the same conditions as the film of the unpolished matrix, and each color developed on the surface may be different accordingly.

[0056] Moreover, the step of rinsing is a step of eliminating any hydroxide solution remaining on the surface by rinsing the surface of the matrix after the step of immersing the matrix in the hydroxide solution. In this step, additional formation of the film due to any remaining hydroxide solution may be prevented by removing the hydroxide solution remaining on the surface of the matrix.

[Mode for the Invention]

[0057] Hereinafter, the present invention will be described in further detail with reference to examples and experimental examples.

[0058] However, the following examples and experimental examples are for illustrative purposes only and not intended to limit the scope of the present invention.

Examples 1 to 3.

[0059] A magnesium-containing sample with a size of 1 cm×1 cm×0.4 T, which was prepared as a matrix, was degreased by immersing in an alkaline cleaning solution, and the degreased sample was immersed in a 10 wt% NaOH solution at 100 °C for the time shown in the following Table 1. Thereafter, the sample was rinsed using distilled water and dried in a drying oven, and a wavelength conversion layer formed of chromium (Cr) was formed using a sputtering method to prepare a color-treated sample. Further, an arbitrary point A existing on the obtained sample which was color-treated was selected, and thicknesses of the film and the wavelength conversion layer at the point A were measured 3 times using a transmission electron microscope (TEM) to calculate an average thickness.

[Table 1]

	Immersion time	Average thickness of film	Average thickness of wavelength conversion layer
Example 1	20 seconds	35±2 nm	40±2 nm
Example 2	10 minutes	130±5 nm	40±2 nm
Example 3	15 minutes	150±5 nm	40±2 nm

Example 4.

[0060] A magnesium-containing sample with a size of 1 cm×1 cm×0.4 T, which was prepared as a matrix, was degreased by immersing in an alkaline cleaning solution, and the degreased sample was immersed in a 10 wt% NaOH solution at 100 °C for 20 seconds. Thereafter, the sample was rinsed using distilled water and dried in a drying oven, and a wavelength conversion layer formed of chromium (Cr) was formed using a sputtering method. The wavelength conversion layer was coated with a matte clear coating material in a liquid phase, and dried in an oven at 120 to 150 °C to prepare a color-treated sample. Here, a thickness of a matte clear coating layer was about 25 µm.

Comparative Example 1.

[0061] A magnesium-containing sample with a size of 1 cm×1 cm×0.4 T, which was prepared as a matrix, was degreased by immersing in an alkaline cleaning solution, and the degreased sample was immersed in a 10 wt% NaOH solution at 100 °C for 15 minutes. Thereafter, the sample was rinsed using distilled water and dried in a drying oven, and a wavelength conversion layer formed of chromium (Cr) was formed using a sputtering method to prepare a sample including the sequentially stacked film and wavelength conversion layer. An average thickness of each of the film and the wavelength conversion layer formed on the matrix was about 150±5 nm and 220 nm, respectively.

Experimental Example 1. Evaluation of coloring efficiency of substrate according to type of hydroxide solution

[0062] In order to evaluate a coloring speed and the coloring power of a color-treated substrate according to a type of a hydroxide solution, the following experiment was performed.

[0063] Magnesium-containing samples with a size of 1 cm×1 cm×0.4 T were degreased by immersing in an alkaline cleaning solution, and the degreased samples were respectively immersed in a 10 wt% NaOH solution at 100 °C for 40 minutes, 1 hour and 2 hours. Thereafter, the sample was rinsed using distilled water and dried in a drying oven, and colors developed on the surface were evaluated with the naked eye.

[0064] As a result, it was determined that the sample prepared by immersing in a 10 wt% NaOH solution has a faster coloring speed in comparison with that of a sample prepared by immersing in distilled water as a hydroxide solution. More specifically, the sample prepared by immersing in a 10 wt% NaOH solution was colored to have a silver color after 10 minutes of immersion, and changed to a yellow color, and then colored to have an orange color within 40 minutes. However, in the case of the sample in which the immersion time was 40 minutes, it was determined that a color change amount of the surface was slight and a color difference was not so large as compared to a non-color-treated substrate. Furthermore, it was determined that the sample in which the immersion time was 1 hour was gradually colored to have a yellow color, and the sample in which the immersion time was 2 hours was colored to have a yellow color, but the coloring power of the developed color was significantly lower than that of the sample prepared by immersing in a 10 wt% NaOH solution.

[0065] From these results, it can be seen that the color treatment of the substrate performed using a hydroxide solution including NaOH, KOH, Mg(OH)₂, Ca(OH)₂, Ba(OH)₂ or the like, has high efficiency and the color developed therefrom is also uniform.

Experimental Example 2. Evaluation of coloring of substrate according to immersion time

[0066] In order to evaluate a color developed on a surface and color uniformity depending on an average thickness ratio of a film and a wavelength conversion layer of a color-treated substrate according to the present invention, the following experiment was performed.

[0067] When samples are prepared in Examples 1 to 3, a color of a surface was evaluated with the naked eye after immersion in the hydroxide solution. Then, a chromium (Cr) layer was formed, a surface color of a color-treated substrate was evaluated with the naked eye, and measurement of color coordinates in the CIE color space of any three points existing on the samples were repeated 4 times. The average color coordinates (L*, a*, b*) and color coordinate deviations were derived from the measured color coordinates, and the result is shown in Table 2.

[Table 2]

	L*	a*	b*	ΔE*	Tfilm/TML	Color before formation of wavelength conversion layer	Color after formation of wavelength conversion layer
Example 1	53.80	-1.63	0.17	0.71358	0.875	Silver	Black
Example 2	67.89	-9.84	-4.33	0.69650	3.25	Silver	Blue
Example 3	70.91	-9.42	8.50	0.50437	3.75	Silver	Green

[0068] It can be seen that a variety of colors such as an achromatic color such as a black color or the like as well as a blue color, a green color or the like are uniformly developed on the color-treated substrate according to the present invention.

[0069] Specifically, as a result of evaluating a color of the color-treated substrate with the naked eye, in the case of the substrates of Examples 1 to 3, when only the film is formed thereon, silver colors which is an intrinsic color of metals are maintained, and when the wavelength conversion layer is further formed on the film, a black color, a blue color or a green color was developed according to the average thickness ratio of the film and wavelength conversion layer. On the other hand, in the case of the sample prepared in Comparative Example 2, it was confirmed that a color was not developed on the surface because the average thickness of the wavelength conversion layer formed on the film was too large, and silver color which is the intrinsic color of chromium (Cr) forming the wavelength conversion layer was developed.

[0070] Further, referring to Table 2, as a result of measuring color coordinates of any three points existing on the sample, it was determined that a color coordinate deviation ΔE* of the substrate of Examples 1 to 3 was 0.7 or less, which indicates that a difference in colors developed on the surface is not large, and color is uniform. Moreover, in the case of the substrates of Examples 1 to 3, each average thickness ratio T_film/T_ML of the film to the wavelength conversion layer was respectively 0.875, 3.25 and 3.75, all of which satisfy the condition of Expression 1. From these results, it can be seen that the color-treated substrate according to the present invention may develop a diversity of colors such as an achromatic color such as a black color, a grey color or the like as well as a blue color, a green color or the like on the surface of the substrate by forming the nanometer scale film and wavelength conversion layer having a specific ratio, and a color may be selectively developed in accordance with the average thickness of the film.

Experimental Example 3. Evaluation of physical properties of color-treated substrate having top coat formed thereon

[0071] In order to evaluate corrosion resistance and adhesiveness of the color-treated substrate having a top coat formed thereon, the following experiment was performed.

[0072] The color-treated sample of Example 4 having a top coat formed thereon was uniformly sprayed with 5 wt% salt water at 35 °C using a salt spray tester (SST), and surface corrosion resistance of the sample; and adhesiveness between the color-treated substrate and the top coat formed on the surface were evaluated after 72 hours of spraying salt water had passed. Here, the adhesiveness was evaluated using a cross-cut tape test method. More specifically, the adhesiveness was evaluated using a method, in which a coated top coat was cut to have 6 vertical cuts and 6 horizontal cuts intersecting one another and formed at 1 mm intervals using a knife, the tape was firmly attached to the intersection points of the vertical cuts and horizontal cuts, and the area of the top coat which is detached when the tape was quickly detached with respect to the total area of the sample was measured.

[0073] As a result, it can be seen that the color-treated substrate having the top coat formed thereon according to the present invention has excellent corrosion resistance, and outstanding adhesiveness between the color-treated substrate and the top coat. More specifically, it was determined that no deformation of the surface due to corrosion occurred in the case of the sample having a matte top coat formed thereon in Example 4. Further, as a result of evaluating the adhesiveness of the sample on which a corrosion resistance test was performed, it was determined that the area of the top coat which is detached due to the tape is 5% or less based on the total area of the top coat.

[0074] From these results, it can be seen that the color-treated substrate having a top coat formed thereon according to the present invention has excellent corrosion resistance as well as outstanding adhesiveness between a color-treated substrate and a top coat.

[0075] Accordingly, the color-treated substrate according to the present invention can maintain the intrinsic texture and gloss of metals of a substrate, improve the durability of the substrate and uniformly realize a variety of colors including a blue color, a green color, an achromatic color such as a black color on the surface of the substrate by including a nanometer-scale film and wavelength conversion layer which have a specific ratio on the substrate, and thus can be usefully used in the fields of building exterior materials, automobile interiors, and particularly electrical and electronic component materials, such as mobile product frames, in which a metal material is used.

[Industrial Applicability]

[0076] The color-treated substrate according to the present invention can maintain a texture of metals and gloss of a substrate, improve durability of the substrate and uniformly realize a variety of colors including a blue color, a green color, an achromatic color such as a black color on the surface of the substrate, and thus can be usefully used in the fields of building exterior materials, automobile interiors, and particularly electrical and electronic component materials, such as mobile product frames, in which a metal material is used.

Claims

1. A color-treated substrate, comprising:

a matrix containing magnesium;

a film formed on the matrix and containing a compound represented by the following Chemical Formula 1; and

a wavelength conversion layer formed on the film:

        [Chemical Formula 1]     M(OH)_m

where M includes one or more selected from the group consisting of Na, K, Mg, Ca and Ba, and m is 1 or 2,
wherein a condition of the following Expression 1 is satisfied with respect to an arbitrary point A existing on the wavelength conversion layer:

where T_film represents an average thickness of the film at the point A, T_ML represents an average thickness of the wavelength conversion layer at the point A.

2. The color-treated substrate according to claim 1, wherein an average thickness of the wavelength conversion layer is 200 nm or less.

3. The color-treated substrate according to claim 1, wherein, when an average thickness ratio T_film/T_ML of the film to the wavelength conversion layer is in a range of 0.1 to 6.0 and an average thickness of the film is less than 80 nm at the arbitrary point A existing on the wavelength conversion layer, L* is 60 or less in a CIE average color coordinate of any three points included in an arbitrary area with a width of 1 cm and length of 1cm existing on the wavelength conversion layer.

4. The color-treated substrate according to claim 1, wherein, when an average thickness ratio T_film/T_ML of the film to the wavelength conversion layer is in a range of 0.2 to 4.0 and an average thickness of the film is in a range of 80 to 140 nm at the arbitrary point A existing on the wavelength conversion layer, L* is more than 60 and b* is less than 5 in CIE average color coordinates of any three points included in an arbitrary area with a width of 1 cm and length of 1cm existing on the wavelength conversion layer.

5. The color-treated substrate according to claim 1, wherein, when an average thickness ratio T_film/T_ML of the film to the wavelength conversion layer is in a range of 0.7 to 8.5 and an average thickness of the film is more than 140 nm and 300 nm or less at the arbitrary point A existing on the wavelength conversion layer, L* is more than 60, a* is -5 or less and b* is 5 or more in CIE average color coordinates of any three points included in an arbitrary area with a width of 1 cm and length of 1cm existing on the wavelength conversion layer.

6. The color-treated substrate according to claim 1, wherein the film includes magnesium hydroxide (Mg(OH)₂).

7. The color-treated substrate according to claim 1, wherein the wavelength conversion layer includes one or more selected from the group consisting of metals including aluminum (Al), chromium (Cr), titanium (Ti), gold (Au), molybdenum (Mo), silver (Ag), manganese (Mn), zirconium (Zr), palladium (Pd), platinum (Pt), cobalt (Co), cadmium (Cd) or copper (Cu) and ions thereof.

8. The color-treated substrate according to claim 1, wherein the matrix further includes stainless steel or titanium (Ti).

9. A method of color-treating a substrate, comprising:

a step of forming a film on a matrix containing magnesium; and

a step of forming a wavelength conversion layer on the film,

wherein a condition of the following Expression 1 is satisfied with respect to an arbitrary point A existing on the wavelength conversion layer:

where T_film represents an average thickness of the film at the point A, T_ML represents an average thickness of the wavelength conversion layer at the point A.

10. The method according to claim 9, wherein the film is formed by immersing the matrix containing magnesium in a hydroxide solution in the step of forming the film.

11. The method according to claim 10, wherein a temperature of the hydroxide solution is in a range of 90 to 200 °C, and immersion time is 20 minutes or less.

12. The method according to claim 10, wherein the hydroxide solution includes one or more selected from the group consisting of NaOH, KOH, Mg(OH)₂, Ca(OH)₂ and Ba(OH)₂.

13. The method according to claim 10, wherein a concentration of the hydroxide solution is in a range of 1 to 80 wt%.

Drawing