JP4062684B2 - Black clear painted metal plate utilizing the metal base appearance - Google Patents

Description

【００２７】
【発明の効果】
以上に説明したように、最大粒径，アスペクト比が規制された鱗片状黒色顔料は，基材・金属板の沿面方向に沿った配向性でクリア塗膜に分散しているため、少量配合でも鮮やかな黒色を発する。しかも、厚みを１μｍ以下としているので鱗片状黒色顔料が半透明になって隠蔽力が弱められ、基材・金属板の金属光沢が観察される。このようにして、金属素地外観を活かしながら黒度を高めたクリア塗装金属板は、従来の黒色顔料によって色調を付与した塗装金属板とは明らかに異なる外観を呈し、内装材，表装材，家電機器用ケーシング材等として広範な用途に使用される。
【図面の簡単な説明】
【図１】 黒色付与に使用するカーボンブラック１の理想的な分散形態（ａ）及びカーボンブラック１が凝集したストラクチャー４となって分散しているクリア塗膜（ｂ）
【図２】 カーボンブラック１のストラクチャー４により黒度低下，白ボケが生じることを説明する図
【図３】 クリア塗膜２に分散させた鱗片状黒色顔料６が基材・金属板３の沿面方向に配向している状態（ａ）及び鱗片状黒色顔料６の面積占有率が高いことを説明する図（ｂ）[0001]
[Industrial application fields]
The present invention relates to a black clear painted metal plate having excellent design properties used for a cover material, an interior material and the like.
[0002]
[Prior art]
As a cover material for home appliances, OA equipment, etc., a painted metal plate with a clear coating has begun to be used. Clear painted metal plates exhibit an appearance that utilizes metallic luster, creating an atmosphere that cannot be obtained with conventional colored painted metal plates. A conventional clear-coated metal plate is manufactured by applying a clear paint containing a colorant to the surface of a painted original plate and baking and drying it. When a dye is used as a colorant, an organic pigment is usually used because it tends to change color during baking and the color tone is not stable.
In a color clear coating containing an organic pigment, a specific wavelength component of the light incident on the coating is absorbed by the organic pigment, and the remaining incident light is reflected by the surface of the base metal plate. A specific color tone develops.
[0003]
The amount of incident light that is transmitted through the color clear coating film is absorbed by the organic pigment depends on the amount of pigment contained in the coating film, in other words, the thickness of the coating film. The absorption is less. For this reason, the color tone to be developed is highly dependent on the film thickness, and the color tone is likely to fluctuate slightly even with slight film thickness fluctuations. The variation in the color tone is emphasized as color unevenness when the clear painted metal plates having different production lots are put together.
[0004]
[Problems to be solved by the invention]
The present inventors have proposed in Japanese Patent Application No. 2001-376893 that a coloring pigment is dispersed in a clear coating film instead of an organic pigment in order to suppress variation in color tone according to the film thickness. In a clear coating film in which a coloring pigment in which a scaly inorganic substrate is coated with a transparent or translucent metal oxide film is dispersed, light incident on the coating film is reflected on the surfaces of the scaly inorganic substrate and the metal oxide film. An optical path difference occurs in the reflected light from the scale-like inorganic substrate and the metal oxide film, and an interference color appears due to the light interference action according to the optical path difference.
[0005]
In color clear coatings that develop color with colored pigments, light-absorbing substances such as organic pigments do not exist in the clear coatings, and are reflected on the surfaces of the substrate, metal plate, scale-like inorganic substrate, and metal oxide coating. The total amount of light is approximately equal to the amount of incident light. Therefore, the developed color tone is not affected by the film thickness of the clear coating film, and there is no decrease in brightness.
In the process of various investigations and examinations of the color clear coating film in which the color pigment is dispersed, the present inventors dispersed the scaly black pigment instead of the color pigment, and the blackness decreased (in other words, the color tone It has been clarified that a color tone with a clear black color is imparted while utilizing the appearance of the metal substrate without causing white blur. Furthermore, as a result of studying the influence of the scaly black pigment on the blackness, the present invention has been achieved.
[0006]
[Means for Solving the Problems]
The present invention has been completed based on the knowledge that the blackness of a clear coating film is greatly influenced by the shape of the flaky black pigment, and even when a small amount of flaky black pigment is dispersed, the clear coating film The purpose of the present invention is to provide a clear painted metal plate that has a stable blackness and has a clear black color tone while utilizing the appearance of the metal substrate.
[0007]
In order to achieve the object, the black clear painted metal plate of the present invention is a scale having a maximum particle size of 20 μm or less, an aspect ratio of 20 or more, and a thickness of 1 μm or less on a clear coating provided on a substrate / metal plate. The black pigment is dispersed, and the scaly black pigment is oriented in the creeping direction of the substrate / metal plate. It is preferable that the scaly black pigment is dispersed in the clear coating film at a ratio of 0.3 to 20 parts by weight with respect to 100 parts by weight of the solid content of the clear paint.
[0008]
[Action]
When black is imparted to a clear coating film by dispersion of carbon black, which is a typical black pigment, white blur tends to occur in the developed color tone. The present inventors have inferred the cause of white blur as follows.
[0009]
In order to develop a clear black color, it is necessary to form on the substrate / metal plate 3 a clear coating film 2 in which carbon black 1 having a small particle size is dispersed. In order to increase the amount of incident light Lin absorbed, a small amount of fine particle carbon black having a primary particle size of about 0.07 to 0.02 μm and a large specific surface area per unit weight is added to the clear paint to clear it. Ideally, the carbon black 1 is uniformly dispersed in the coating film 2 (FIG. 1a). The incident light Lin that enters the clear coating film 2 in which the particulate carbon black 1 is uniformly dispersed is partially absorbed by the carbon black 1 at the absorption point P on the surface, and is cleared as reflected light Lout with reduced light intensity. The light is emitted from the coating film 2. The black surface is recognized by observing the reflected light Lout.
[0010]
However, the carbon black 1 tends to aggregate and it is difficult to uniformly disperse the carbon black 1 in the clear coating film 2. The carbon black 1 distributed in the clear coating film 2 usually has a structure 4 in which fine particles aggregate with each other in a chain and grow three-dimensionally (FIG. 1b). Carbon black 1 tends to agglomerate into secondary particles having a relatively large particle size as the primary particle size decreases.
The formation of the structure 4 means a decrease in the surface area of the carbon black 1, and hence a decrease in the number of absorption points P. As a result, the absorption of the incident light Lin decreases and the amount of the reflected light Lout increases. As the amount of light increases, the blackness of the clear coating film 2 decreases, and white blur is observed.
[0011]
The uneven distribution of the carbon black 1 proceeds in accordance with the formation of the structure 4, the ratio (area occupancy) of the carbon black 1 occupying the surface of the clear coating film 2 decreases, and the surface portion 5 without the carbon black 1 increases ( 2a, b). Incident light Lin that has entered the clear coating film 2 on the surface portion 5 reaches the surface of the substrate / metal plate 3 without being absorbed by the carbon black 1 and is observed as reflected light Lout having substantially the same light amount. Accordingly, the total amount of the reflected light Lout increases, and the blackness of the clear coating film 2 decreases.
[0012]
In the present invention, black pigments that hardly aggregate in the clear coating film 2 were investigated on the premise that the formation of the structure 4 is a cause of a decrease in blackness and white blurring. As a result, when a flaky black pigment with a regulated maximum particle size and aspect ratio is used, the flaky black pigment is uniformly dispersed in the clear coating film 2, and the reduction in blackness and white blur are effectively suppressed. I found it. The suppression of blackness reduction and white blur caused by scaly black pigment is presumed as follows.
[0013]
The scaly black pigment 6 blended in the clear paint has high dispersibility and orientation, and the surface of the substrate / metal plate 3 and the in-plane direction of the scaly black pigment 6 are almost parallel (FIG. 3a). Therefore, the probability that the incident light Lin reaches the scaly black pigment 6 is increased, and the absorption rate of the incident light Lin is significantly increased as compared with the clear coating film 2 in which the structure 4 is distributed. And since the area occupation rate of the flaky black pigment 6 which occupies the surface of the clear coating film 2 is large, there is little incident light Lin which permeate | transmits the surface part 5 without the flaky black pigment 6, and reaches the base material and the metal plate 3 The total light amount of the reflected light Lout decreases. As a result, the incident light Lin is efficiently absorbed, and blackness reduction and white blur are suppressed.
[0014]
Effective absorption of the incident light Lin becomes remarkable with the scale-like black pigment 6 having a maximum particle size of 20 μm or less and an aspect ratio of 20 or more. Such scaly black pigment 6 includes graphite, molybdenum disulfide, and the like.
As the maximum particle size decreases, the uniform dispersion of the scaly black pigment 6 with respect to the clear coating film 2 proceeds, and the color tone of the clear coating film 2 stabilizes. However, since an excessively small maximum particle size tends to adversely affect the orientation of the scaly black pigment 6 along the creeping direction of the substrate / metal plate 3, a maximum particle size of 1 μm or more is preferable.
[0015]
In order to orient the scaly black pigment 6 along the creeping direction of the substrate / metal plate 3, the scaly black pigment 6 having a larger aspect ratio is more preferable. Further, when the thickness is 1 μm or less, the flaky black pigment 6 becomes translucent, and part of the incident light Lin may pass through the flaky black pigment 6 and reach the substrate / metal plate 3. That is, the hiding power of the scale-like black pigment 6 is weakened, and the metal base appearance can be utilized. In addition, even when the light reflected by the surface of the substrate / metal plate 3 is emitted to the outside as reflected light Lout, the probability of being absorbed at the absorption point P of the scaly black pigment 6 is high, and the reflected light Lout As the amount of light decreases, bright black appears.
[0016]
The area occupation ratio of the scale-like black pigment 6 per unit weight of the clear coating film 2 increases as the aspect ratio increases. Therefore, even if a small amount of scale-like black pigment 6 is dispersed in the clear coating film 2, the incident light Lin and the reflected light Lout are efficiently absorbed, and a color tone with high blackness is imparted to the clear coating film 2. However, the scaly black pigment 6 having an aspect ratio exceeding 1000 is not practical because it is expensive and requires attention in handling, and the transparency of the pigment itself increases and it is difficult to obtain black. The scale-like black pigment 6 having an excessively large aspect ratio tends to partly protrude from the clear coating film 2 and adversely affect the smoothness of the coating film surface.
[0017]
Embodiment
Since the base material / metal plate 3 is used in a product form utilizing the appearance of the metal substrate, stainless steel, various plated steel plates, aluminum, aluminum alloy, copper, copper alloy, magnesium, magnesium alloy, etc. are used. . Prior to the formation of the clear coating film 2, an appropriate pretreatment such as degreasing, pickling, chromate treatment, phosphate treatment, and chromium-free treatment is applied to the base material / metal plate 3.
[0018]
The clear paint for forming the clear paint film 2 does not impose any particular restrictions on the paint type, but is highly transparent acrylic, polyester, urethane, polyolefin, fluorine, epoxy, vinyl acetate. Organic resin paints such as chloroprene are used.
The scale-like black pigment 6 to be blended in the clear paint is not limited by the material as long as the maximum particle size is 20 μm or less and the aspect ratio is 20 or more, and the black pigment has a color such as red or blue. Can also be used. Specifically, scaly black pigment 6 marketed as GRAPHITAN 7525, GRAPHITAN 7700 (manufactured by Ciba Specialty Chemicals) or the like is used.
[0019]
The scale-like black pigment 6 has a blending amount for the clear paint determined according to the required blackness, but is selected from a range of 0.3 to 20 parts by weight with respect to 100 parts by weight of the resin solid content under normal conditions. The It is an advantage of the scaly black pigment 6 that a color tone with high blackness can be obtained even with a small blending amount, and the tendency becomes more prominent as the scaly black pigment 6 having a larger aspect ratio is used.
In addition to the scale-like black pigment 6, a rust preventive pigment, a colored pigment, a dye, or the like may be added to the clear paint as needed within a range that does not impair the transparency of the clear coating film 2.
[0020]
Prior to the formation of the clear coating film 2, a primer clear coating film containing no scaly black pigment may be formed in order to improve the adhesion to the substrate / metal plate 3. The primary clear paint does not impose any particular restrictions on the type of paint, and epoxy resin, epoxy-modified polyester resin, urethane resin, urethane-modified epoxy resin, or the like can be used. The primary clear coating film further improves the adhesion between the base material / metal plate 3 that has been subjected to a coating pretreatment such as chromate treatment and the coloring pigment dispersion clear coating film 2. The primary clear coating film is preferably formed with a film thickness of 1 to 10 μm.
[0021]
The scaly black pigment 6 blended in the clear paint for forming the clear coating film 2 is produced by pulverizing the raw material with a ball mill, a rod mill or the like. The aspect ratio of the scaly black pigment 6 can be adjusted by controlling the thickness with the rotational speed and rotational speed of the mill and classifying the maximum particle size with a sieve or the like.
[0022]
After applying a clear paint containing scale-like black pigment 6 to the coating original plate, depending on the resin type and application amount of the clear paint, the clear coating film 2 is formed by heating at 200 to 400 ° C. for 30 to 120 seconds. -It is baked on the metal plate 3. Observing the resulting clear painted metal plate, the metallic luster of the base material / metal plate 3 is utilized, and the metallic luster that gives an inorganic cold feeling is softened by the clear coating film 2, so the appearance of a mild color tone It becomes. In order to obtain a stable color tone, it is preferable to form the clear coating film 2 with a film thickness of 5 to 20 μm.
[0023]
A top clear coating film can be further formed on the clear coating film 2. The top clear coating film covers the scaly black pigment 6 protruding from the surface of the clear coating film 2 and stabilizes the color tone. Furthermore, by improving the smoothness of the coating film surface, the sharpness is improved and a high-class feeling is imparted. The clear paint for forming the top clear coating film is not particularly limited, but the same or similar paint as the clear coating film 2 is preferable. Specifically, acrylic, polyester, urethane, polyolefin, fluorine, epoxy, vinyl acetate, chloroprene, and other organic resins with high transparency, or resins and inorganics that form these shrink patterns An organic resin blended with a polymer can also be used.
[0024]
Since the coated metal plate with the clear coating film 2 may be processed into a product shape, the clear coating film 2 or the top clear coating film has excellent adhesion to the substrate / metal plate 3 and the flexibility of the coating film itself. As required. Scratch resistance is sometimes required as a function contrary to flexibility. A clear paint resin system is selected in consideration of the characteristics according to the purpose.
When the same or similar base resin is used for forming the clear coating film 2 and the top clear coating film, the paint baking conditions can be set substantially the same, or the temperature at the time of baking the top clear coating film can be set slightly higher. Therefore, the scaly black pigment dispersion clear coating film 2 is softened when the top clear coating film is baked, and the scaly black pigment 6 dispersed in the clear coating film 2 is aligned in the in-plane direction of the substrate / metal plate 3. Reoriented to form. Since the surface area of the scaly black pigment 6 effective for light absorption is increased by reorientation, a color tone with high blackness can be obtained. Making the base resin the same or similar is effective in increasing the affinity between the clear coating film 2 and the top clear coating film and preventing delamination.
[0025]
【Example】
A stainless steel plate with a polished pattern having a thickness of 0.4 mm subjected to hairline polishing was used as a coating original plate. The paint original plate was pickled with a 2% hydrochloric acid, it was subjected to surface treatment of acid to form a chromate film of Cr equivalent coating weight 20 mg / m ² in coating type chromate treatment.
Next, a clear paint in which a scaly black pigment 6 having a maximum particle size ≦ 20 μm, an aspect ratio ≧ 20, and a thickness ≦ 1 μm was applied to various coating bases on a pre-painted coating original plate, and the maximum reached plate temperature of 230 ° C. was 60 ° C. By heating for 2 seconds, a clear coating film 2 having a dry film thickness of 5 to 20 μm was formed.
The brightness of each clear-coated steel sheet obtained was measured, and the influence of the maximum particle size and aspect ratio of the scaly black pigment 6 on the blackness of the clear coating film 2 and the degree of utilization of the metal substrate appearance were investigated. The blackness was expressed as a lightness L value, and the utilization of the metal substrate appearance was evaluated by the appearance of the hairline pattern on the coating original plate.
For comparison, the blackness and the degree of utilization of the metal substrate appearance were similarly investigated for clear-coated steel sheets on which the clear coating film 2 was formed under the same conditions except that carbon black was used as a black pigment.
As can be seen from the investigation results in Table 1, it was confirmed that the scaly black pigment 6 was dispersed in the clear coating film 2 to exhibit an appearance utilizing a metal base appearance with a clear black tone without white blurring. .
[0026]

[0027]
【The invention's effect】
As explained above, the scaly black pigment with the maximum particle size and aspect ratio regulated is dispersed in the clear coating with the orientation along the creeping direction of the base material / metal plate, so even in a small amount A bright black color is emitted. In addition, since the thickness is 1 μm or less, the scaly black pigment becomes translucent, the hiding power is weakened, and the metallic luster of the substrate / metal plate is observed. In this way, the clear-painted metal plate that increases the blackness while taking advantage of the appearance of the metal substrate has a distinctly different appearance from the painted metal plate that has been colored by conventional black pigments. Used as a casing material for equipment for a wide range of applications.
[Brief description of the drawings]
FIG. 1 is an ideal dispersion form (a) of carbon black 1 used for imparting black color, and a clear coating film (b) in which carbon black 1 is dispersed as an aggregated structure 4
FIG. 2 is a diagram illustrating that blackness is reduced and white blurring occurs due to the structure 4 of carbon black 1. FIG. 3 A scaly black pigment 6 dispersed in a clear coating film 2 is a creeping surface of a substrate / metal plate 3. State (a) oriented in the direction and diagram (b) explaining that the area occupancy of the scaly black pigment 6 is high

Claims (2)

  A scaly black pigment having a maximum particle size of 20 μm or less, an aspect ratio of 20 or more, and a thickness of 1 μm or less is dispersed in a clear coating provided on the substrate / metal plate, and the creeping direction of the substrate / metal plate A black clear painted metal plate that takes advantage of the appearance of the metal substrate, characterized in that the flaky black pigment is oriented.   The black clear painted metal plate according to claim 1, wherein the scaly black pigment is dispersed in the clear coating film at a ratio of 0.3 to 20 parts by weight with respect to 100 parts by weight of the solid content of the clear paint.

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